Hazardous Materials

12 = • . I

. 7 ~, Chemistry of Some Hazardous Organic Compounds: Part 1 ,c,--1\ ' -= -->~, - I l

!W tJi m - ' ~ i I

Courtesy of Eugene Meyer.

i:iW4iUA acute mye/ogenous leukemia, p. 498 aliphatic hydrocarbon, p. 469 alkane, p. 470 alkene (olefin), p. 476 alkenyl group, p. 477 alkylate, p. 507 alkylation, p. 506 alkyl group (alkyl substituent), p. 472 alkyne, p. 479 allyl group, p. 477 antiknock agent, p. 507 aplastic anemia, p. 498 aromatic hydrocarbon, p. 469 aryl substituent (aryt group), p. 496 asphalt, p. 506 asphalt kettle, p. 506 aviation gasoline, p. 508 benzyl group, p. 496 biomagnification (bioamplification), p. 525 boilover, p. 504 bottled gas, p. 488 BTX, p. 496

carbon-carbon double bond, p. 468 carbon-<arbon single bond, p. 468

466

•:. ' - :·

carbon-carbon triple bond, p. 468 catalytic uacking, p. 483 cetane number, p. 510 chlorofluorocarbon (CFC), p. 516 common name, p. 470 common system of nomenclature, p. 470 compressed natural gas (CNG), p. 486 condensed formula, p. 470 cracking, p. 483 crude petroleum (crude oil; '"crude·), p. 503 cydoalkane (naphthene), p. 471 cydoalkene, p. 476 degreaser,p. 515 dehydrogenation, p. 492 dielectric fluid, p. 523 diene, p. 476 diesel oil (diesel fuel, gas oll), p. 505 endocrine disrupter, p. 523 endocrine gland, p. 523 ethyl group, p. 472 fractional distillation (fractionation), p. 504 Freon (Freon agent), p. 517 geometrical isomerism, p. 478

halogenated hydrocarbon (alkyl h,1llde, aryl halide), p. 573 heating oll {fuel oil), p. 511 heavy naphtha, p. 504 heterocydlc compound, p. 500 hormone, p. 523 hydraulic fracturing (tracking), p. 483 hydrocarbon, p. 469 hydrotreatment, p. 510 IUPAC name, p. 473 IUPAC system of nomenclature, p. 473 kerosene, p. 505 knocking, p. 507 light naphtha (ligroin), p. 504 line marker, p. 484 liquefied natural gas (LNG), p. 486

liquefied petroleum gas (LPG), P· 487

lubricating oll (lubricant), p. 505 methane hydrate, p. 483 methanogenesls. p. 482 methyl group, p. 477 methylene group, p. 472 mid-grade gasoline, p. 509 mineral oll transformer, p. 524

motor gasoline, p. 508

n•tur"I gas, p. 480 non-PCS transformer, p. 524 ll"propYI group, p. 472 octant number (octane rating), p. 508 organization of Petroleum Exporting countries (OPEC), p. 503 ortho· (o-), meta- (m·), and ~f,l· (p-), p. 495 ,ca-contaminated transformer, p. 524 pCB transformer, p. 523 pttrothemkal, p. 513 petroleum coke, p. 573

iMii,10¥5

petroleum distillate, p. 504 petroleum gas, p. 504 petroleum products, p. 503 petroleum refinery, p. 5o3 phenyl group, p. 496 polynuclear aromatic hydrocarbon (PAH),p. 499 premium-grade diesel oil, p. 517 premium-grade gasoline (supreme and su~r unleaded), p. 509 rtformation,p. 497 regular-grade diesel oil, p. 511

regular-grade gasoline (regular unleaded), p. 509 saturated hydrocarbon, p. 470 sour crude, p. 510 Stockholm Convention on Persistent Organic Pollutants (POPs treaty), p. 527 structural Isomerism, p. 470 thermal uacking, p. 483 trlene, p. 476 unleaded gasoline, p. 510 unsaturated hydrocarbon, p. 476 vinyl group, p. 477

Associate the physical and health hazards of the organic compounds noted in this chapter with the information provided by their hazard diamonds and GHS picrograms.

I Discuss the manner in which a carbon atom covalently bonds to nonmetallic atoms including other carbon aroms.

I Describe the nature of carbon-carbon single bonds, carbon-carbon double bonds, and carbon-carbon triple bonds.

I Describe the chemical bonds that exist in molecules of the hydrocarbons. I Illustrate that most hydrocarbons have structural isomers but only those with carbon-

carbon double bonds have geometrical isomers. Memorize and apply the rules for naming simple alkanes, cycloalkanes, alkenes, dienes, trienes, cycloalkenes, cyclodienes, cyclocrienes, and alkynes. Describe the nature of the line markers required by DOT to identify the approxi- mate loca tions of natural gas and petroleum transmission pipelines. Identify the types of liquefied petroleum gas that are available for commercial use as bottled gas.

1 Identify the general nature of the labels required by the U.S. Federal Trade Commis- sion on compressed natural gas and liquefied petroleum gas dispensers when these substances a re provided to customers for potential use as alternative motor fuels.

1 Describe generally the manner in which acetylene is containerized in steel cylinders fo r storage and transportation.

1 Name the simple aromatic hydrocarbons and their derivatives when provided with their molecular structures and vice versa. Identify the most common ways by which emergency responders are likely to be exposed to polynuclear aromatic hydrocarbons (PAHs). . . Identify the petroleum products that are produced by the fracuonation of crude petroleum. .

1 Provide the molecular structures of the halogenated hydrocarbons havmg one and two carbon atoms per molecule and provide acceptable names for them. Identify the primary risks assoc iated with exposure to the halogenated hydrocarbons

havin? one and two carbon atoms per molecule. hi rofluorocarbons. Describe the molecular nature of the most common c 0 Identify the principal ways in which chlorofluorocarbons and related substances

Were formerly used · d k f I Describe the nature. of the markings that EPA requi res on conramers an ran so

ozone-depleting subsrances. Chapter 12 Chemistry of Some Hazardous Organic Compounds: Part I 467

I _I/

carbon-<arbon single bond A shared pair of electrons between two carbon atoms

carbon-ca rbon double bond Two shared pairs of electrons between two carbon atoms

carboo-<arbon triple bond Three shared pairs of electrons between two carbon atoms

Describe rhe mokcul~u srruccures of the polychlorinated biphenyls (PCBs) Identify the primary reason ih~t PCBs are "? longer manufactured in the United ldenrify the locations in a typical commumty where emergency responders are ~t•"" ro encounter PCB transformers. . k~i)' Describe the nature of rhe markings that EPA requ ires on PCB-containing dectri ('QUipment. . caJ ldenrify che labels, markings, and placards 1hat DOT requires on packa . organic compounds noted in this chapter and the transport vehicles use~1? of th~ shipmenr. or their

0 rganic compounds are constituents of many commercial products in I d' ing and motor fuds, solvents, plastics, resins, fibers, su rface coatings cu f 1_ng h~,. textiles, and explosives. The fact 1hat they are used so widely undersc~~:sr:i:rants, to srudy them in some derail. netd_

1\,lany org:mic compounds of commercial interest are flammable gases or fla liquids. ft is hardly surprising t_o !ear~ that many organic compounds are burning w~:~bk a.re encountered at cra~~rtanon m1sha~s an~ other emergency scenes. Although the t ry rial for fire and explosion 1s generally their primary hazard, exposure to o rganic co Po en. may also pose a heahh risk. Prolonged exposure to certain organic compounds mPound.s variety of acute and chronic health effects that includes damage to the liver, kidn~~ a hean; depression of the central nervous system; and the onset of cancer, ' d

This chaprer is an introduction to the study of organic compounds and the propcnj f hydrocarbons and halogen.ated hydrocarbo~s that are commonly encountered commerC:u0,. Chapters 13, 14, and 15 discuss the propemes of more complex organic compounds. )

12.1 WHAT ARE ORGANIC COMPOUNDS? The molecules of all organic c_ompounds have one common fearu re: the presence of one or more carbon atoms. In most mstances, the carbon atoms share electrons with other non• metallic atoms. As shown by their molecu lar structures in Figure 12.1, methane, carbon tetrachloride, carbon monoxide, and carbon disulfide are exa mples of o rganic compounds having molecules in which the ca rbon atoms are bonded ro other nonmetallic atoms.

Carbon atoms can also mutually share electrons with other ca rbon atoms. When the molecular structures of such compounds are examined, we fi nd that two carbon atoms can share electrons to form any of the following: carbon-<arbon single bonds /C-C); carbon-<arbon double bonds (C=C); and carbon-<arbon triple bonds /C=C). Carbon- carbon single, double, and triple bonds consist of one, two, and three pa irs of shared electrons, respectively, between rwo carbon atoms.

Figure 12.2 illustrates the bonding in molecules of erhane, ethylene, and awylcne, each of which has two carbon atoms. Molecules of erhane have carbon-carbon single bonds, molecules of ethylene ha\'e carbon-carbon double bonds, and molecules of actt) · lene have carbon-carbon triple bonds.

H I

H-C- H I

H \1ethlnc

Cl I

CI - C- CI I

Cl Carbon 1u r..1Chlomk

Cas o

C.lrt,011 niono\1dc Cnrbond1 ,u lfi dc.-

FIGURE 12 · , A carbon atom may share 1ts electrons with the electrons of hydrogen chlorine, orygen. anoi~· fur The com pounds that resul1 from this electron sharing are methane, carbon tetrachlor,de, carbon mon-OJ.oe and carbon d,sulf,de, respectively

468 Chapter 12 Chemistry of Some Hazardous Organ ic Compounds: Part J

I

- c- C- 1 I

H H I I

H- c- C- H I I H H

- c ase-

H- CasC- H

: ,~~URE 12 ·2 Two carbon atoms may share their form ~~ns in lone of three ways, resulting ,n the carboni~n ° ,carbon-carbon s,ngle bonds. carbon- bo d Oub.ebonds, andcarbon-<arbon tnple • n 1 1Nhen carbonatoms unite w1thhydrogen

a,oms.fhe compoundsthatresult are ethane ethene (ethylene), and ethyne (acetylene), respect,v~ly

The cova lent bonds between carbon atoms i h l nds may be linked into chains · I d' n t e mo ecules of more complex organic

~0111~u arbon skeleton of the follow·' me u mg I branched ch~ins, or into rings. Consider ~~s;a\ :ncd (b): mg two mo ecules noted m the following ill ustrarion

- C- C- C- C- C- c - - c - c - c-c-c- c - 1 I C C

l•l lb)

In (a), the carbon atoms are bonded to one anorher in a continuous chain, whereas in (b), the carbon atoms are bonded to one another in a branched pattern. This means that car- bon atoms bond n_ot only_to other carbon atoms in long chains bur also ro groups of other carbon atoms as side chains attached to the main chain.

Aside from being bonded t~ other carbon atoms, each carbon atom displayed in either a straight- or a branched-cham manner is typically bonded to one o r more atoms of hydrogen, oxygen, nitrogen, sulfur, or a halogen. For instance, when the ca rbon atoms in [he compound having the carbon skeleton (a) are bonded to hydrogen atoms, the molecu- lar structure of the compound is written as follows:

H H H H H H I I J I I I

H-C-C-C- C- C- C- H I I I I I I H H H H H H

When che ca rbon atoms in (b) are bonded to hydrogen atoms, the molecular structure of rhe compound is written as fo llows:

H H H H H H I I I I I I

H- C-C-C- C- C- C- H I I I I I I H H H H I I I I H- C- H H- C- H

I I H H

There arc many orga nic compounds that consist of continuous or branched chains of carbon atoms. The actu:i l number of such compounds appears to be virtua lly unlimited. More than 6 mill ion organic compounds are already know~. . .

\Y/e begin the study of organic compounds by exammmg the simplest group, the hydroca rbons. These are compounds whose molecules ar~ composed of only ~ar~n and hydrogen atoms. All hyd rocarbons are broadly divided mto two _groups: aliphatic and aromatic hydrocarbons. Aliphatic hydrocarbons are nona~omanc hydrocar~on;- aro_matic hydroca rbons are a group of.compounds_chara;;~:::~:/r~~s~:;~r/~n u~~re their molecular structures: They conram benzene rings. detail in Section 12. 11.

compound whose mol- ecules are composed solely of carbon and hydrogen atoms

aliphatic hydrocarbon Any compound com·

posed of molecules having only carbon and hydrogen atoms that are not arranged in benzeneorabenzene- likestructure

aromatic hydrocarbon Any compound whose

molecules are composed solely of carbon and hydrogen atoms, at leastsomeofwhlchare structurally similar to benzene

Chapter 12 Chemistry of Some Haza rdous Organic Compounds: Part I 469

--,

I I

I I

s::::tin

a lltane • AAy hydrocar- bon having molecules in which the carbon atoms are bonded wlely as carbon-carbon single bonds (C--C) or (C-H) bonds

Sil tur.at~ hydrocarbon Any hydrocarbon

having molecules that are composed solely of C-< and C-H bonds

structural isomer- ism • The phenomenon associated with com- pounds whose mole- cules have the same atoms but differ in the manner in which the atoms are structurally arranged

common system of nomenclature • The system used historically for the naming of organic compounds

common name The historical name for an organic compound

condensed formu la • The formula of a compound in wh ich symbols of the atoms are written ne1rt to the symbols of the atoms to which they are bonded and in wh ich dashes are omitted or used only in a limited fashion

12.2 ALKANES AND CYCLOALKANES An alkane is a hydrocarbon in whose molecules the carbon atoms are bonded cit hydrogen atoms or to other carbon atoms solely by means of carbon-carbon si

1 htr I()

The general chemica l formula of an a lkane is C,,H2,,~1, where II is a non:z;g e.boni.h. When the number of carbon atoms is only I, the n~mber of hyd~ogen atoms i~ ~~:c&tt responding compound is n:imed methane. Its chem1ca l_formula 1s Cl-14. When the nu c0r. of carbon atoms is 2, _the num_ber of hydro~en atoms 1s 6. T he cor responding comPo~~r is named ethane, and us chemica l formula 1s C2. H6- lld

The alkanes are called saturated hydrocarbons, because the four bonding cl each carbon atom are shared with the bonding electrons of four othe~ atoms. The~~:n~~f to be saturated with hydrogen. Several examples of the alkanes having from

00 . d

carbon atoms are noted in Table 12.1. Their names and formulas should be mem~~~~gh1

12.2-A FORMULAS OF THE ALKANES The molecular st ructures liste~ in Table 12.1 are straight~ch~in ar~angements for tilt alkanes having from one to eight carb?n atoms, but beg1nnmg wuh butane, several branched-chain arrangements ma y be written as well._ Buta~e molecules have four carbon atoms per molecule, which can be represented by their Lewis structures as follows:

H H H H H H H I I I I I I I

H-C-C-C-C- H H- C- C- C- H I I I I I I I H H H H 7 7

H-C- H I H

In the first structure, the fo ur carbon atoms are bonded to one another in a continuous chain. In the second structure, only three carbon atoms are bonded in a continuous chain. The fourth carbon atom is bonded co the carbon atom in the middle of the chain.

Because there are two correct ways to write molecular st ructures for the formula C; H 10, they represent two distinct compounds. To distinguish them by name, 1he com- pound having the ca rbon atoms bonded in a continuous chain is called n-butane, whmas the compound with the branched structure is named isobutane.

The phenomenon associated with two or more compounds that have the same molC\- ular formula but different structural arrangements of t heir atoms is ca ll ed structural isomerism. One way by which strucrural isomers are identified is with an 11- (for "nor- mal" ) in front of the name of the compound that contains a continuous chain of carbon atoms, and iso- (meaning " the same") in from of the name of the compound that hasa methyl group (CH3-) bonded to a carbon atom next to the terminal (end) carbon a1om. This system generally is referred to as rhe common system of nomenclature, and thr names of the compounds are called common names.

. Ahhough a m?lecular structure may be written for a ny alkane, it ge nera lly is conve- nient to condense It by simply writing the symbols of rhe atoms next to the symbol ofihr carbon arom to which they are bonded. When writing the formula for an alkane, the S)'m· bols of rhe hydrogen atoms are written next to rhe symbols of the carbon atoms to which they are bonded. The formulas derived in this manner are called condensed formulas. For example, the condensed formulas for 11-butane and isobutane are noted here:

CH3CH2CH2CH3 \11-Butanc) CH3-y H-CH3

Cl-1 3 1~obu1:rnc

470 Condensed fo rmulas convey the same bonding information as the more complete Lewi> strucrures, bur rhe dashes are either entirely omitted o r used only in a limited fashion.

Chapter 12 Chem istry of Some Haza rd ous Organic Compounds: Part 1

• ·HlfaCUM,.;;;;,;p.;; · u·ennv::·nw::IJVEle:w·w ·,01::r N.AME t,-1ettiane

Utiane

propane

Butane

Pentane

Hexane

Heptane

Octane

Nonane

Decane

MOLECULAR FORMULA LEWIS STRUCTURE CH,

I C2H6

C1Ha

Ci.H10

CsH12

C6H14

C1H16

CsH,a

C10Hn

I

H I

H- C- H I H

H H I I

IH- C-C - H I I H H I H H H I I I

H-C-C- C- H I I I H H H

H H H H H H l \ \ I 1 I

H-C- C- C- C-C-C- H

I I I I I I \ HHHHHH \

HHHHHHH 1 I I I l 1 l H- c- c- c- c- c- c- c-H l \ \ \ I l \ HH HHHH H

I HHHHHHHH I I I I I I I I H- c- c- c- c-c-c- c-c-H \ I I I 1 I \ I H H H H H H H H

HHHHHHHHH

\ CONDENSED FORMULA

I CH,

\ CH ,CH,CHa

I CH ,CH,CH ,CH, \ CH ,CH ,CH ,CH, CH a

I I I I I I I I I H- C- C- C- C- C- C- C- C-C-H

I I I I I I I I I I H H H H H H H H H

I

12.2-B FORMULAS OF THE CYCLOALKANES cydo,lkano (oaphthml I . I f h lkanes in which the fi rst and last carbon atoms • Any hydrocarbon _t IS possible to write formu as o_r t ea . d h other in a cyclic arrangement. whose molecules ar in a cont inuous chain are chemically hnkel hto the petroleum industry, they are composed of a eye.lie These compounds are ca lled cycloalka~es , ah: ~l~~n::, the cyc\oa\kanes are saturated ring of carbon-<arbon more commonly called naphthenes . Like t single bonds

hydrocarbons. h . t oi Some Hazardous Organic Compounds: Part I 471 Chapter 12 C emts ry

r I

I

~I

alkyl group {alkyl substituent} • Any grou p of atoms having the general chemical formu la C,,Hz,, . 1 obtain@d by rem~ving a hydrogen atom from the formu la for an alkane

methyl group • The designation for the group of atoms CHr

ethyl The des- ignation for the group of atoms CH1CHr

n-propyf The designation for the group of atoms CH3CH20·!z-

The general chemica l. formula of th e cyd o:ilkanes is C,, 1-12,, . C hemists narne th placing the prefix C)'clo- m from o f the name of the parent hydroca rbon. Thus, th:rn ti, plest cyd oaJkanes are cydopropane, cyclobutane, cyclo pentanc, and C}'clohexane s1rn.

Sometimes the str_u~tural ~ormulas for cyclopropanc, cyclo burane, and cyclo~en are represented by wrirmg a mangle, square, and pentagon ~or C.3 H6, C.d-fs, and C ;anr respectivel y. The structural formu la of cyclohexane (C6 H 1.z) 1s represented by tv,, s 1,, fo rmula s called its boat and chair co,rformations. 0 unique

6 0 8 C)dopropant· C)clobutafll.' C)clop,:nt:an,: (bo.111 C)cloh,.,~an"

(d1.11r1

In chis text, the chair conformation solel y is used to represent cyclohexane.

12 .2-C THE IUPAC SYSTEM OF NOMENCLATURE When a hydrogen atom is remo ved from an alkane, the resulting group is ca lled an alk

1 group, or alkyl substituent. Their general chemical formu la is C., H zn+ 1• The most fa mir. iar examples are the meth yl group, et hyl group, and n-propyl group.

- Cl·l-i - C/-l2CH3 - CJ·l2CH2CH3 \kth)lgtou11 Eth)lgroup ,, . Prop)l group

The names of che common alk yl subsriruems arc provided in Table 12.2 .. These names and their molecular formula s should be memorized.

MH/iifW Some Common Alkyl Substltuents NAM E• I CHEMICA L FORMULA Methyl

Ethyl

n-Propyl

lsopropyl - - ---r-' -:C-CH2CH1CH3, or C3H0,-_________ _

CHrfH- , or (CH3)1CH- CH3

-,-"·-,-•u_tyc-l;--------rl - cH2CH2CH2CH1, Of(4H_, -___ _ Jsobutyl CH3

I - CH2 rH, or (CH 3)iCHCH2 -

CH3 sec-ButyJb

tert-Butyl b----

CH3 7-, or(CH3lJ C - n-Pentyl' ----

- CH2CH2CH,CH2CH1, or(5H11- -- %e alkyl group~ a re named by replacing !he -ane suffix ~ ent hydrocarbon w!th -yf. . If it is

:~~~r~i:~;o;h~or 7ahi~~na : ,~~'.1~~~~1P:~m~;~~1 :~et:~1~:r~~~r:~:~. si; c~ns~~~~;;~e;~: J · and ~ bonded to three carbon atoms, ,1 Is ten la ry (!ert-). 'Also called n•am~I.

472 Chapt er 12 Chemistry of Some Hazardous Organic Compounds: Part 1

Although the simple h)'drocarbons genera lly f he complex hydroca rbons are difficult to name :;~nr\~~r:d to by 1hei r common names, 1

To o vercome this hurdle, a second S}'stem f g I

ommon system of nomenda - 1~re. le and systemat ic . It was adopted b the 1~ nom:nc anire_was devised that is both ~~:rnistry (IUPA C) an? is called the 1J'PAC sy;~~:t~~n~~~:;n of Pure and Applied org;i nic compounds deri ved from the use of this sys1em are calledc:~~~~-n:~e;ames of

In the IUPAC syStem, the following rules apply to the naming of alkancs fr~m their molecular structures:

1 Locate th~ longeSt chain of carbon atoms in the structure. This is called the " main chain .• , It is not necessary ~hat the main chain be written horizontal!}' to be continuous.

1 Assign numbers consecut1vely to each carbon atom in the main chain starring from the end that gives _1~e alkyl substituents attached to rhe chain the smaller numbers.

1 Designate the posmon of each subsciruent by the number of the carbon atom along the main chain to whic h it is attached.

1 Name the subs1itu~nts alphabetically (ethyl before methyl, and so on) and place the names of rhe subsutuents as prefixes on the name of the main chain,

1 If several substituents occur in the same compound, indicate the number of identical groups by the use of the following prefixes before the name of the substituent: di- for rwo identical groups, tri- for three identical groups, tetra- for four identica l groups, and so on. The prefixes di, tri, tetra, sec, and tert are ignored when alphabetizing the substituents, but the prefixes iso and cycfo are not ignored.

The use of these IUPAC rules of nomenclature is illustrated in Table 12.3.

FiH!ifii Examples of Using the IUPAC Rules for Naming Alkanes When Their Chemical Formulas Are Known A.LKAN E

3-Methylheptane

2,2-Dimethylbutane

2.4-Dimethylhexane

l Ethyl-4-isopropylheptane

5-Ethy l-2,S-d imethylheptane

CHEMICAL FORMULA

CH3CHi-TH- CH 1

CH, I CH, I CH, I CH,

CH, I

CH3- T- CH2CH 1

CH3

CH3-TH- CH2-TH- CH3

CH 1 TH2 CH3

CH3

CH3-tH-TH- CH2CH, CH1

CHJCH2-CH-CH; CH3

CH2CH1

CH CHi - t- CH2CH2- TH -CH1 1 ~HJ CH i

IUPAC system of

internationally recog- nized system used to name organic compounds

name of an organic compound derived from use of the IUPAC synemofnomenclature

. of Some Hazardous Organic Compounds: Part I Chapter 12 Chemistry 473

r f r ,~ I

474

SOLVED EXERCISE 12.1 Using the IUPAC sys1em. name the -,11:ane having the fol/ow,ng condensed formula

(H1 -CH -CH2-fH - CH1 -CH1

(Hi TH; CH

Solution: :t ~den;,~:hr:~~l:s'~hn;;~~~~~~;~~~; ~a~:~1:;~50f ~e::~:•:;~~~~51~:~c;;i~~;n c~ ~::.~:,, of ~h':7dngest chan rtot~

I 2 J • S 15 (HJ-7H-CH2-7H-CH;-CH1

(/-13 y"Hz CH;

we see that me methyl group 1s bonded 10 the carbon atom numbered 2, and the ethyl group is bonded ID carbon atom numbt'f'eo' 4 Because tne a•~yt substituents are named ,n alphabetical order, the comPCIIJnd !l::. rectly named 4~thy1•2-methy/hexane

bt<au~st~:~~~~~nngu:~~~~1::~~g:~ 0 ::~~~~ ;;~;

0ai:; ;:~:~t:~~;~~~1~~t~~n°~~;,~b; :c: methyl group and 3 for the ethyl group) Hovvever, 11 Is correct to number the longest chain of carbo., atoms ~ e1therofthtfol/owmg ways

1 J 4 5 6 CH3 - fH-CH1-;H-CH1 -CH1

1CH3 y"H1 CH;

2 l • (H3 - CH -CH1 - CH - CH1 -Cr-13

I I 1CH3 5(H1

I 6CH1

The use of erthtrof these numbenng schemes also g;ves 4"('thy1•2-methylhexane as the correct name of this coml)CUIO'

SOLVED EXERCISE 12.2

7hf' detalled analysis of a commercial rubber solvent proV1des the followin9 approximate chemical compos1oon

f•) 50% by volume 1s a m1lCture of 2,3.0imethylbutane, 2,3-dimethylpentane. and 3,3-dimethylpenlil~. (bJ 30% 1s a mixture of 2.2-d,metnylbutane, 3•methylpentane, 2,2-dimethylpentane, methylcydoptntarit,

methykydoheXc1ne, 1.2-d,merhylcyclopemane, n-hexane, and n-heptane. and lcJ 20% 1s a mlXtlJre of n-butane, n-pentane, and 2,4--dimethylhexane wr1tethechemrcalf°'mulaforeachsubsr.ance

Solution: The solvent's corutrtuents have the following condensed formulas (;ii) CH1 CH1

I (H3- ·H - (H -(H3

13-0'TTE'l)bu1,1r,e

CH; I

f""H (H "(-(H1(H,

CH; JO<rrethy,~n!Jn,

fH3 fH1 CH3-CH-CH-CHzCH3

l J-0,melh)lperi\Jne

Chapt er 12 Chemistry of Some Hazardous Organic Compounds: Part J

(b) 1H' CH1-1 (H1('13

CH; ll-O">eth)-h;1,T<1"('

CH, I

CHJ-1-CH1CH;CH1

CH; 22-ome1n,per,t.:me

~CH;

w ethykyclohex<1ne

(d ( H3(HzCH1CH3 n-8U!.!f11'

CH3- TH-CH2 ~ 1H - CH;(H3

CH3 CH1 1 4-0memy!he.>..lne

T'"'l (H3(H2-(H -CH1CH1

J-~•etn~•oenwne

0-cH, lv'ethylcycloperu~ne c/·

1.2-0,methtcyi;loPtnt~-ie

CH3CH1CH1CH1CH; n--Pe<11.dne

12.2-D TRANSPORTING A LKANES AND CYCLOA LKANES When shippers offer an alkane or cycloa lkane for transportation, DOT requires them to encer the relevant shipping description on an accompanying shipping paper. Some exam- ples for severa l rep resentative alkanes and cycloalkanes a rc lis ted in Table 12.4. DOT also req uires shippers and carriers to comply with all applicable labeling, marking, and plac- arding requi rements.

Fhiiifii Sh1ppmg Oesrnpttons of Some Representative Alkanes and Cycloalkanes ALICANE OR CYCLOALKA NE SHIPPING DESCRIPTION

Butan,

Cyclohexane

Ethane

Methane, compressed

Methane, cryogen ic

Natural gas, compressed

Natural gas, cryogenic

Petro leum gases, liquefied

Propane

UN1011, Butane, 2.1

UN1145, Cydohexane, 3, PG II

UN1035, Ethane, 2.1

UN1971 , Methane, compres~d, 2.1

UN1972, Methane, refrigerated liquid, 2.1

UN1971, Natural gas, compressed, 2.1

UN1972, Natural gas, refr igerated liquid, 2.1

UNl075, Petroleum gases l iquefied, 2.1 o, UNl075, Liquefied petroleum gas, 2.1

UN1978, Propane, 2.1

Chapter 12 Chemistry of Some Hazardous Organic Compounds: Part I 475

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alkene (olefin) • Any hydrocarbon h.JVing molecules tha t contain a t le,1.st one carbon-- carbon double bond (C=O

unw1uro1 tedhyclrocar- bon • Any hydro-carbon whose molecules con- tam at least one carbon-- carbon double bond o r tnple bond (C=C orC=C)

cyclo.alhne • Any afkene w hose carbon ;, toms are bonded to each othe r in a cyclic fash ion

12.3 ALKENES, DIENES, TRIENES, CYCLOALl<Ellles CYCLODIENES, AND CYCLOTRIENES •

Hydroca rbons whose mol« ules conram one or more carbon-<:a rbon double bon called alkenes, or olefins. Beca use the molecular structure o f each alkene is defi,

1 ds ~,r

hvdrogen acorns rdarive ro 1he molec ular structure of the corresponding lk en1 tn alkew.-s .:i re sai d ro be unsaturated hydrocarbons. Like the cycloalka.nes, the arke~;e, the the general chenucal formula C,.H_,:,, . s h.. it

The simples t alkene is _n:1med ethe_ne, or more.~o~monl y, ethylene. Its molecular mula is C:H.i , and 1rs Lewis structure 1s the fo/lo\\ rng. for

H H I / C= C I \

H H

The presence of the carbon--car';><>n double bond i_n the str~cture restricts the moverneni o f the atoms about the bond. This means that the six atoms m the ethylene molecule lie in the !>.:lme plane.

T~ere are also alken_es in which rhe first and last carbon atoms in a continuous chain a re jo rned to each o th~r rn a cyclic arrangement . They are ~ailed cyclo~lkenes. Their gen. era.J chemical fo rmula 1s CM H;M - ; . They are named by placing the prefix cyclo- in front of the na me of the parent alkene. The three simplest cycloalkenes are cydobutene, crdopen. rene, and cyd ohexene. Their chemical formula s often are represented by using appropn- a re geometrical designs as shown here:

0 0 CJcloOOtcoc C)clopen1,:nc C).: lohc., cnc

diene • Any hydrocar- bon w hose mo lecu les have two carbon- c<11rbon do uble bonds

The molecules of alkenes can also have multiple carbon-carbon double bonds. When rhey ha ve rn•o and three double bonds, the compounds a re called dienes and trients. respectively.

triene Any hydrocar- bon whose molecule s have three carbon- ca rbon d ouble bonds

12.3-A STRUCTURAL ISOMERISM IN ALKENES Ethene and propene do not ha ve structural isomers. For example, rhe condensed formulJ for propene ca n be correctly represented in eith er of the following wa ys:

Bec:iuse either formul:t 1s 1hc other one turned around end for end, it is a rcpre~ntJt!On of rh e same substa nce.

Howe\·er, we ca n write the fo llowing rhree condensed formula s for the strncrurnl JSO· mers of 1he alkene having the formu la C.~ 1-18,

ln the fi rst two fo rmula s, th e ca rbo n atoms are displayed in a co ntinuous chain. Tht molecu la r s tructures differ o nly by the position of rhe carbon-carbon double bond. Th e ih ird fo rm ula differs in rha1 ch c carbon atoms arc bonded to one anoth('r in a b ra nched p ::m crn.

476 Chapter 12 Chemistry of Some Hazardous Organic Compounds: Part I

3 B NAMING ALKENES. DIENES TRJE 12. • cvcLoO1ENEs, ANO CVCLOTRIEN~:s. cvc toALKENes,

niisrs use rhc -e11e suffix to name alkenes C ~ : members of the a lkene series are named. et~:1~:qu::11: , in ihe IUPAC system, the fi r~t ~ 111111011 names arc ethylene, propylene, butylene, a:y~;~~u:; ~e::r~v~rntene. Their

I~ the IUPAC S)'Stem, n~t only is _the -ene suffi x used to identfr,, an aik.ene but the ros1non °1f

the dou~ct bood m tlhk r- mam cha in of its molecules also is indicated .• The fol- lo"1ng rues are use o name a enes:

I Consec_ud~ely number rhe car~on atoms in the main chain of continuous carbon atoms b)' begrnmng at the e~d that 1s ~ie~rer the double bond. The carbon-carbon double bond must alwa_y~ be included withrn the main chain of continuous carbon atoms. ]odr,1care the pos1t10n of the carbon-carbon double bond by the appropriate numerical pre 1x.

~:s~:~~ec~~~/t:s!'.~~:~tei:t 0

~l~~~'.tuent by the number of the carbon atom along

For example, the compounds having the fo rmulas CH2::CHCH2CH3and CH3CJ !=Cl /C l I; ue named I -butene and 2-butene, respectively. The compound having the formula CH2 =T-CH3 CH ,

1s named isobutenc, isobutylene, or 2-merhylpropene. The name used exclusively in com- merce is isobutylene.

When dienes and trienes are named, the positions of rhe carbon-carbon double bonds are denoted with appropriate numbers, and diene or trie11e is used as rhe relevant suffix . The following examples illustrate the naming of a diene and a triene:

CH2=CI I - C!-l = CH2 CH3-CH= CH - G i = CH - CH= CH~ l .3• 1lurnd1cne I J.S. fkpt.1tncrn:

An alkrl derivative of a cycloal kene, cyclodiene, and cyclotriene is named by using one or more numbers to identify the location of the alkyl group relative to the location of the double bond. For example, the compounds designated by the following molecular srructures are named 1-meth ylcyclopentene and 3-met hylcyclopentene;

o-Cll3 o-Cl-13 1-,\lc th)k} , lop,:n tene

The atoms in the carbon-carbon double bond of a cydoalkene are always numbered I ~nd 2. Consequently, as 1he name of a q 'cloalkane, methylqdopentene may be preceded only b)' a 1-, 3-, or 4-.

Finall>·, just as there arc a lkyl groups, there are also alkenyl groups: The three most common ly encou ntered alkenyl groups are the methylene group , vinyl group, and allyl group .

,\klh)kn,·,ruup Vin)l grnup ,\ll ) l group

Ahhough the vinyl and ally! groups :ire basc_d on alkenes, th;a~:~y~~:~~~~: ;i3k:~ 1 ~ ,~

conrain a carbo n-carbon double bond because It h_as ~~l~ro:~ic com ounds such as the groups are used in the common system to name sunp g P chlorinated derivat ives of methane, ethcne, and propene,

CH::Cl2 CH2=CH - CI CH2=CH - CH~- Cl M clh)lcncchlonJc (D1chlornn1elh.1ncJ

V1n~l chl0n<k A ll ) l <.hl ,mdc (Chh.:nwthenc ) {\-Chloni propcocl

noncycl ic group of atoms having either the formula - CH1- or t he general chemical formula C,,H~, wheren .- 2

methytene group • The designation for the group of atoms -CHi -

vlnyl The des- ignation fo r the group of atoms CH1=CH-

desig- nation for the group of atoms CH1= CH-CHi-

Chapter 12 Chemistry of Some Hazardous Organic Compounds: Part I 477

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geometnQI lsomuism • The phenomenon assoeiatedwith compounds whose moleculeshawthesame atoms but d iffer in the manner in which they are spatia lly bonded about a carbon-carbon double bond

12.3-C GEOMETRICAL ISOMERISM IN ALKENES The relari\'e rigidiry of the ~arbon~arbon double bon~ leads to a new kind of iso . call ed geometrical isomerism. This phenomenon anses when 1he two substicu:erisll! atoms are different on each c-jrbon arom that makes up the ca rbo n-ca rbon d b n1s or for ex.ample, nrn Lewis srruc1ures can be written for 2•butene as follows: ou le bond.

\H3 c-c I I

H CH; muis-2-Buicnc

\HJ 5='·!3 c-c I I

H H ru-2-Butcnc

These structures illusrrate that a hydrogen atom and a methyl grou p are bond d carbon atom in the carbon-ca rbon double bond. Because they are bonded toe th~o ~ach carbon atoms in each Lewis structure, they do not rep resent structural isomer . mt arrangement of their atoms differs in space. When two compounds have the sa~ )Ct th( tural formula but differ by the spatial arrangement of their atoms, they are ca ll:dst: metrical isomers. g

Geometrical isomers are named by using either of the prefixes trans- or ds- m . on the opposite and same side. oft.he carbon-carbon double bond, respectively. 'A/;~;~ ~~:~cs:e~~c:,p~;i:i~. geometrical isomers of 2-butenc are named trans-2-butene and tis-

SOLVED EXERCISE 12.3

Us,ng the IUPAC system, name the alk:ene having the fo llowing condensed formula

CH1CH2-~ - CH1

CHiHz

Solution: First, 1dentrfy the longest continuous chain of carbon atoms that contains the carbon-<arbon doub:t bond The longest cha n conta;ns four carbon atoms, which s1gnrf1es that the compound 1s a denvatJVe of bu:e~ Ass gn,ng a number to each carbon atom from the nght to the left of this longest cha,n. we see that t~ two carbon atoms m the carbon-<arbon doub'e bond are numbered 1 and 2, respectively.

4 1 2 1 CH3(Hz - 7 =CH2

( H3CH1

Th,s means that the compound 1s a dem•at1ve of 1-butene The ethyl group is bonded to t he carbon atom num- be,ed 2 The compound then is correctly named 2-ethyl-1-butene f',Ne do not ass ign a number to each carton :om from the left to the r,ght of the longest chain, because then the carbon atoms in the carbon-carbon cloub't nd

would be numbered 3 and 4 We always ass,gn numbers to the carbon ato ms so that the smclle< numbtri are assigned to the carbon a1oms in the carbon-<arbon double bond )

12 ·3·D TRANSPORTING ALKENES, DIENES, TRIENES, CYCLOALKENES,

CYCLODIENES, AND CYCLOTRIENES :hen ship~ers offer an a lkenc, diene, t ricne, cycloa lkenc cydodicne or q •dotricnc for acc~:;;~~~/:;~h~O: re~uires them ro corer the releva~t shipping :description °~ ;: listed in Tab[ 12 Pf Jcj per. Some examples for se\•era l representarn·e compound h applicable lab:lin · ~a ! also requires ~hippcrs and carriers to compl)' with all or er

g, rkrng, and placarding requirements Chapter 12 Chemistry of Some Hazardous Organic Compounds: Part I .

iHifii ALKENE, DIENE, TRIENE, OIi CYCLOALKENE

sutadlenes, stabilizeda

1-Buteneb

, 11.2-Buteneb

u,1ns•2•Butene~

1,s,9-Cydododecatriene

cycloheptatnene

cyclohexene

Cydopentene

o,i1obutylene, isomeric compounds'

Ethylene

Hexadienes

1-Hexene

1-Pentene

Propylene

Shipping Descript f Dienes, Tnenes, a~~~;1::i;;:~::presentat1ve Alkenes,

SHIPPING DESCRIPTION

UN1010, Butadienes, nabilized, 2.1 UN1012, Butylene,2 .1

UN1012, Buty1ene,2.1

UN1012, Butylene, 2.1

UN2S18, 1,5,9-Cyclodode<:atriene, 6.1, PG Ill (Marine Pollutant) UN2603,Cycloheptatriene, 3, PGII

UN2256, CycloheJ1.ene, 3, PG II

UN2246, Cyclopentene, 3, PG II

UN2050, Diisobutylene, i1omeric compounds, 3, PG 11

UN1962, Ethylene, 2.1

UN2458, Heudienes. 3, PG 11

UN2370, 1-Hl'Jl.ene,3, PG II

UN 1108, 1-Pentene,3, PG I

UN1077, Propylene, 2.1

' Pi.or to. the ir shipment, OOT requires the addit ion of a subnance to 1,2· arid 1,3-butadiene to lnhiblt their aui:o- l)O!ym,nzat lon and thereby promote th, lr stab111 zatlon (Sl'alon 14.]). 1Fo1pu1posesofOOTregulat lom, t-butene, c/1-2-butene, and tram•2·butenearede1lgnated "butyl, ne • ' for purposes of DOT regulat ions, dllsobutylene refers to .i, mhctuf t of the compounds 2,4,4-tr lmtthyl-i-pentene ,lld2,4,4-trimethy l-2-pentene.

12.4 ALKYNES Hrdrocarbons having one or more ca rbon-<arbon triple bonds are called a\kynes. Like the alkencs, they a re unsa turated hydrocarbons. The genera l chemical formula of an alkyncis C., H2,, _ 1,

The simplest member of the a lkyne series has the fo rmula C21-12• It is named ethync in the IUPAC system, but it is known more generally as acetylene, its common na me. The Lewis structure of acetylene is denoted as fo llows:

In the common system, alkynes are named as dcriva1ives of acetyle~c . If an alkyne is represented by either of the general fo rmulas R-C=C- H or R-C=C-R , the correspond- ing compound is named by identifying the alkyl groups, Ra nd R' , in their formulas. Thus, the derivatives of acetylene having one and two methyl groups are named mcthylacerylcne and dimethylacety lenc, respectively.

,\kth) l~CCI) k m: Dunc th) l:iccl~ knc

In the IUPAC system the alkynes are named by replacing the -ane or -~ne suffi~ o.n the associated alkanc or ~lkene, respectively, with th~ s:~:l::·rh: ~~a7nc~~::t~~f~:

1 ~~

Used lo indicate the position of the carbon-ca rbon tnpl . h 1 1 f 1 tinllous ca rbon atoms. Consider the two alkync isomers havrng t c mo ecu ar ormu a

bon whose molecules have at least one carbon-<arbon tr iple bond (OEC)

Chapter 12 Chemistry of Some Hazardous Organic Compounds: Part I 479

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G H ., . The compound n;uned 1_-butyne is the isomer in whic~ the carbon-<'arho bond is loc.ued between a terminal ca rbo n atom a nd the one munediatel d " n tr% The compound named 2 -buryne is the C~ H6 isomer in w hich the carbo~..:;:bent10

1 l

bond 1s located ben\·een the rwo nonternunaJ carbon atoms. on trip]r

H - C .:; C - CH~CH1 CH3- C =: C - CH , l -BUl)OC ! -HUt)nc

Although an alkyne may have structura l isomers, it do~s nor have geometrical is In the IUPAC system, the alk ynes are named by usmg the following rules: oniers.

Con~ utively number the carbon ~toms i~ the main chai_n of cominuous carbo by beginning at the end of ~e cham ~ at_ 1s neare~ the ~1ple bond. The carbo 11 :uorns crip!e lxmd must_ ~ways be rnc_luded within the main cha_m of continuous carbo~rbo.i Indicate the posmon of the triple bo~d by the appropriate numerical prefix. tOJn.i

by the number of the carbon atom along

SOLVED EXERCISE 12.4

natu ra l gas • The flammable gas- primar ily consis-ting of methane-formed in nature by the decomposition of an imal and plant life

Using the IUPAC system, name the a11cyne having the following condensed formula

CH3-CH - CHi -C :C -H CH, CH,

Solution; F1m. determine that the longest continuous cham of carbon atoms containing the carbon-cafbon a-,. p!e bond has so,; carbon atoms This s,gn1fi1."S that the compound ts a derivat ive of 1 •he)(}'ne. Next, ass ign numOI!~ to the carbon atoms from the right to the left and then downward. The two carbon atoms 1n the carbon-urb.:iti tnp!~ bond are &,en nuMbered 1 and 2, respectively

' 3 2 1 CH3-1H-CH2-C=-C-H sSHi 6CH3

Becaus~ the methyl group 1s bonded to the carbon atom numbered 4, the compound 1s correctly namt~ 4-methyl-1--hexyne

12.5 NATURAL GAS (METHANE) The simple aliphatic h ydrocarbon s are flammabl e gases. They are most common])' encoumered as domestic and industrial fuels. The simplest of rhem is methane, whose chemical formula is CJ-Li. Methane is the primary constituent of natural gas, roug~l)' 70% by volume. The chemica l industry uses narural gas as both a feedstock and an tn· plant energy source.

N atural-gas-fired power plants are used co produce electricity. T hese plants no,~' prof duce approximately 25 % o f the electricity used by Americans . A lthough the operat'.0 " ~ . narural-gas-fired power planis is not pollution -free it is a more en vi ronmentally fn~nd ) practice when compared to the operation of eithe; coal-fi red or oil-fired power plant~ figure 12.3 illustrates char natural-gas fired power plants produce less poll ution 30 fewer greenhouse gases.

The ~merican elect ric utilit y industry's swi tch from the use of coa l to n~cu r~~~~'. substantia ll)' reduced the atmosphe r ic carbon dioxide concentration during ~

480 Chapter 12 Chemistry of Some Hazardous Organic Compounds: Part t

!'.:r~i:~ed~;\~:::tit~;/~;~;~tbon dioxide emi ssions from energy genera tion in 20 l2

~-!_ethane COnSti_tutes IO% to I~% of the greenhouse gases linked to global warming. As noted m Table 5.3, ICs_global wa rming potential m·er a 20-year time period is 72. This GWP rtflects that metha,~e 1s much more potent as a greenhouse gas than carbon dioxide.

Pure methan: is an odorless, colorless, tasteless, and lighter-than•air gas. Some of its phrsica l properties are provided in Ta_ble 12.6. Although odorless, when natura l gas is encountered by emergency respon~ers, tt usually possc:ssc:s a slighdy offensive smeU caused b)· the presence of sulfurous organic compounds that have been added imentionally

10 assist

!)(l'SOnnel attempting to detect gas leaks. As shown by the data in Table 12.6, when methane is mixed with air, it burns at con-

ccnm1cions between approximately 5% and 15% by volume, producing a slightly luminous f\lme and relea sing 958.1 Btu/ft3 (39,820 kjlm3) to the surroundings. Fire and explosion JTC its primary ha za rds.

Methane can pose a health hazard as an asphyxiant (Section 10.3-A). Individual s who inhale the gas for a prolonged period lose consciousness because they are denied suf• ficienc oxrnen. Prolonged exposure constitu1es a direct threa t to life by suffocation.

~·lethane occ urs primarily in nature as a result of the decay and alteration of animal and plant remains deep below Earth's surface. Consequently, it often accompanies nearby deposi ts of crude petroleum (Section 12. l3-A ), which forms by the same mechanism. ~!ethane is a lso abundant in the atmosphere within coal mines, where it is called ~fire- dJmp. When the mud a t the bottom of stagnant pools, swamps, and rice paddies is dis- turbed, methane bubbles ro the surface. Here, it is called .. marsh gas."

1/li!ifiW Physical Properties of Methane Melting point 801lingpoint

Specificgravityat68°F (20°C) Vapor density (air= 1) Flashpoint

Autoignition point

lower flammable limit Vpper flammable limit Heat of combus-tion [32' F (O"C) and 1 atm}

-297°F(-183"C)

- 25B' F(-161°() 0.42 0.553 -366"F (-221 ' C) 999' F(537' C)

5¾ byvolume 15% byvolume 958.1 Btu/ttl (J9,8201dlm3)

1 U.S. Energy lnforma1ion Admmistration (WJshington, DC).lO!J. . H dous Organlc Compounds: Part l

Chapter 12 Chemistry of Some azar 481

nr ll.S-A METHANE IN THE ATMOSPHERE OF COAL _MINES Sec 7 6 C mechwe 1s one of se,·eral constHucms of coal 1:sr1~~;~10t~~ ~reda:o; )C'eps from seams 1nro the surrounding enclose "·here ir ~ccumubres and pose:; a senous risk of fm: and explosion The of merhane 15 onlv $ % to l5% by volume m :m E\en a small spark can /I

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m1-th.1nogenu i:s • The biological production of methane by anaero- bic bacteria

World\\ rdc.-. thousands 0 ( coal miners are killed annually, en herd flammable merh3.Ile ignm:s \\ irhm a mme, or b} subsequently breathing

hC'rc of carbon monoxide formed when methane and other gases burn ~e Umrc.-d Srates. using the Jeg.:il au rhonty of the Coal Act {Section , e \ Safer} and Health Admiruscraaon (MSHA), a dumon of the U.S Department of ln1,}1nr regulates health and s.ifecy conditions m coal m111es b) means of man dator} standard 1~

Safety standards withm mines address the reduction o f methane and other gases s. guard ag:unsc the porennahry of ha zardous incidents mvolvmg the presence of metba To carbon monoxide, and ocher gases w1chm enclosed mmes, the owners and operaton IJt, coal mmes are required at 30 C F.R 575 330 .. co provrde ven nlatton /within minesJ ;f dilute, render harmless, and to carry away flammable, explosive, noxio us, and har~ gases, dusts, smoke, and fumes. " . . . .

ln 2010, the fui!ure co _comply "."uh this re~ulaaon conmbured to the ~eadliesr c~ mine accident ~x~rienced m the Unued ~tares smce ~970. An earth-sha~er~n~ explosiOQ occurred withm severa l tunnels of a mm~ l~c~ ted m Beckley, West Virginia. Expen\ concl uded char it was triggered by t~e 1gnmo~ of accum ul_ar~d methane and coal du st. 2 As a consequence of the explosion, 29 mmers lost their li ves, 19 from carbon monoxide poison ing.

12 .5-B METHANE PRODUCTION BY THE DECOMPOSITION OF ORGANIC MATTER

Methane is also produced when bacteria decompose organic wastes by means of rh~ anaerobic process called methanogenesis. H ence, methane is the prima ry conscitumi of landfill gas and mamma lian flatulence. Ir is also produced by ca rde and other rumi- nants as rhey digest cellulose-like foods such as grass and s traw. The culprit in thts! foods is actua lly Jignin (Section 14.5-A), a gro up of complex compo unds that exist in and berween plant cdJ walls and provide che plant with its rigidity. The ruminanrs arc unable to easily digest Jignin . The process requires the help of rnicroflora inhabiring cheir guts. Methane is produced as these microflora degrade the lignin , and the rumi- nants belch ir into che atmosphere.

There are 1.8 billion ru minants worldwide. On average, a si ngle cow exhales 634 quarts (600 L) of methane into the air daily. EPA has estimated that approximately 25% of the methane in the air originates with th e belching of livesrock. As amusing as this mJ )' fuse appea.r; the production of methane by livestock has become a serious matter. This fact has caused agricultural scientists to test ways of altering the volume of methane rhar li1·~- srock produce, primarily by providing ruminants wi th dietary adjustments.

The belching of livestock is no r the o nly uncharacteristic way in which the a1mos· pheric methane concentration increases. For example, m ethan e has also been locked in the permafrosr in Siberia since th e last ice age, 10,000 yea rs ago. The wa rming of plantt Earth has caused the Siberian permafrost ro thaw and slow ly release its methane inrorhe atmosphere. 3 Scientists estimate that approximately 9% o f the met han e emissions into rhe atmosphere originate in the Arcric tundra.

;1. DJ ~irt McAtcu, Upper Big BrJnch, Report ro the Gov('rnor (,\by 20 11). NJfJ/Ja ShJkhova er al.. ~Extemi\·e methane ven ting to thr :irmo;phcrr from scdimrnts of rhr Uir SibtnJn

Arctic Shelf,~ SC1enu, Vol. 327 (20JOJ, pp. 1146-1250.

Chapter 12 Chemistry of Some Hazardous Organic Compounds: Part I

11 _s-C INDUSTRIAL SOURCES OF METHANE

l he v;t~d ~;~;;:~~:: 1 ;~:~s8j~r~~;aie\yblS_ trillion cubic fm {~0.7 1 1113 ) of natura l gas

Jllnu,i >·14'% coming from Canada a 1 i:do ~:~~ed from do~1estic _sources, wit h anot her

1 !1e ~etroleum and coal by a process ca lled ,;:: k~~/

11;:1::e, !~a,;k~~so ~LiCed when rn~;~:;;1:icc:ah{k~~oca rbons arc subjected to hig~ tempcr~;ures under r::od· ~;~: •~;f!~i~~e rrJ te press,urelyt·,c c,acking ) g ) or relativel y low tempera tures in 1hc presence of a associated with break.-

nlrst (ca a . • ing down larger, C'J • ;,Ja1ur;il gas gcnera_lly is recri:ved from underground, porous reservoirs where it has :~:;~;d:~:a;~~e ~:t

umulatrd for cenlunes. There 15 a vase wealth of natu ral gas\ rid "d b · 1 k d ecules into simpler and ~;densr rock deep beneath Earth's surface where it often is d~·~ icu~\:'rc~:i:~~- t~c lighter molecules niiddk of t~e la Sr dtcadef th, rc was serious concern chat America would experience a shortage in its su pp ies O natur_a l gas. However. drillers perfected a method to extract nJt11rlll gas from shale_. T he retne~a l method is certa in to boost U.S. gas production for Jrc;1drs to coi:ne, and 15 based 0 ~ imp_le~enting a process called hydraulic fracturing , or fracklng . During the pr~css, dnllers IOJ CC- t a mi xture of water, sand, and chemical prod- ucts under pressure deep into the ground to break up the shale rock forma, ions and nearly impenetrable sa nds to create channels from which the entrained natural gas (and crude

rroleum ) may be recovered.

crackingproceuaccom· plished by the applica- tion of heat

cracking process accom· plished lnthepresence of a catalyst

pe Shale is a fine-grained sedimenta ry rock composed mostly of clay and mud . Shale-rich regions exist in the Appalachian sect ion of the northeastern Uni1ed States, as well as in Trxas and North Dakota. The la rgest known reservoi r of natural gas in the United States is J geologic format ion known as the Marcel lus Shale. It underlies siza ble portions of Wes[ Virginia, New York, Ohio, and Pennsylva nia. The natural gas within thi s one shale may be as much as 490 trillion cubic feet (14,000 km3).s

Natural gas is a lso ava ilable off U.S. shores beneath the seafloor. The U.S. Depa rt- mrnt of Interior estimates that the outer continental shelf holds 420 trillion cubic feet (1 2 trillion m3) of unrecovered natural gas, which, if tapped, could heat America n homes for the next 80 years. Although scientists perceive a benefit in harnessing this resource

h~d raulicfracturing

that involves pumping water laced with sand and chemical products deep underground at high volumes and pres- sure to extract natural gas entrapped in shale

for future use by humankind, activists fear that em•ironmenta l havoc would be wreaked b)· drill ing operations that occur offshore in ultradeep waters.6 Marine microorganisms produce approximately 4% of the methane that ultimately reaches che ocean surfaces and becomes a constituent of the atmosphere.

The prevailing pressure below the sea noor is approximately 30 times the atmospheric norm. Under these condi tions, meth:m e and water molecules coexist in a unique fas hion: The metha ne mo lecules are trapped within "cages" composed of 5¾ water molecules. .\fany cages link together co form white crystals that physically resemble ice. Each unit of the substance, ca ll ed methane hydrate, is represented by the formula CHr5.75 H2O (s ). .\!ethane hydra te is stabl e under pressure, but when brought to the ocean's surface, its units collapse and the methane wafts into the atmosphere.

'U.S. Energy Information Administration (\Vashing1on, DC), 20_13. . . , . Jfor rwo major reasons, hrdraulic fracturing h.u become a subJcct of mten!te cn\·1ronment.1.I scrut~ny. First, the chemical products used in [he process include canccr-uusing substances whose rele.ise 1mo the environment has nrgl tirdy impacted the quality of the groundwater in the regions where the proces!.CS are_conduct~d. Scc?nd, hydraulic fractur ing nor only dislodges natural gas but also compounds of toxic metals hke arsenic, banum, chromium, and zinc, :ill of which are natural components of shlle. The fea r is that 1hesc compounds could le.1th 1n10 1heground111arer andtainritfor fu turegcnerations. . . , , 10ffshorc drilling fo r natural gas and crude petroleum i~ als~ ~otenml!y replete w11h adHrse cm ironmental constqucnces. In 2010, the explosion of an offshore drilling ng m the Gu~f of iM~~~:~e:~u~d t;:xt;:\~~)~! i.~ 1rorkcrsand the rele,1sc ofn:1turalfasandcrudepetroleumthroughamassivcppe Id be. pp d Tl h m1lh~n cubic feet ( J .62 million m _) o~ narural gas was flared ::~=!~rt~;h~~~~/:1~xico, :~:r: 1~ e;~an~::~ rluging oil_ flowed 10ward the barrier islands, marsh~ , and_ be and threatened coastal touri~m in four states. 1rg1onal wildli fe, shut down large areas of commcmal fishing,

m1-thane Ice-encrusted natural gas located in porous rock in the arctic tundra under the permafrost and in the deep-ocean sediments of the continental slope and ocean floor

Chapter 12 Chemistry of Some Hazardous Organic Compounds: Part I 483

line marbr • An aboveground sign ind i• eating the appro~ mate location of a natural- gas-transmiu ion pipeline

\lt th me h ·dr.m deposits :ire fo und not on_ly below ocea~ flo~rs, bur also I.Jnd • ' . } ·h he climaie is especiall y cold. 1Vla1or discoveries f er th,

r~~~~r~::.t~~a;o:n; :~ ~J.isk.i and Si beria. 0 rncthJ~r

l~.S-D NATURAL GAS TRANSMISSION BY PIPELINE Throughout many of rhe lower 48 states, large \'Ol~m~ of nar~rral gas ~re directly trans~ irom pffl'Oleum fidds or refineries by a network ~f p1peli~es _until they ~lunately are dis1nbt'r~ ro individual homes. apamnenr complexes~ busmess bu1ldmgs, chenuca l plants, and na;r~ g:is-fired power pbnts. Approximate-!y 60 ¼ of U.S. households use natural gas 10 Pri/~- the heat on rhe kitchen stovetop a~d ~o fi re_ the_ home _furnace, water hearer, and clothes d '.cit

As it moves through tr::msnuss1on pipelines, n.~rural_ ga~ gradua ll y loses its Pres?~t :rnd \'elocit-y. To o,·ercome these problems, the ~as 1_s penod1cal!y pa~sed through a llu~rt ber of compressor stations located along the p1p~lm~. At each s~at~on, tu rbines reco Ill- press the natural gas to increase rhe ra1e at wh1:h it moves wuhm the pipeline I.Jn7i rt"aching the nexl compressor station . The longest smgle network of natural-gas-iran _ 1 sion pipelines in the United States srre1ches a distan~c of over 13,000 miles (20,909 sk:· during \\'hich it passes through 100 compressor s1a uons. '

When utility and construction workers and emerge~cy r:spo1~ders check for the l)Os- sibility of pipeline damage or interfe rence, t~ey m_ust quickly 1d~nufy the location of naru. ral gas pipelmes. Firsr, rhey generally spot signs li ke the followmg:

HIGH PRESSURE NATURAL GAS PIPELINE SHORE DIGGING IN THE VICINITY, (All YOUR LOCAL GAS COMPANY

(000) 000 0000

Second, ar 49 C. F.R. S 195.410, DOT requires a line marker like that shown in (a) of Figure 12.4 to be posted ar regular intervals along a pipeline, at road and railroad crossings, and a, aU aboveground facilities. The line marker idenrifies 1he approximate location of both abo\'eground and underground pipeline right-of-ways. Its pos ting is intended to al~n

,., lb/ le/ (di FIGURE 12A To alert workers and emergency responde1s of the presence of a natural-gas-transm1ss-on p.ptl 'it DOT requires the ~ng of line markers along a pIpe l1ne 1oute (al ,5 a hne mark.er posted near roads, ra•lroad>. and alcng pipeline nght-of-ways It contains the wo1d WAl!~iNG followed by any of the words PlPEU\ E, GAS , P-PEU",,f , or ~.t.ATURAL GAS PIPEU/\;E, the name of the opera tor, and the telephone number at which theoper~OI' may be reached at all times The line mari:er colors are yellow. black, and red (b) Is an aerial ltne mark.er for~ of by ~ lots of pipeline patrol planes. (c) is a p1pelrne casing vent. and (d) Is a parnted metal or plastic post The defacing, damaging, removing, or destroying any type of pipeline marker 1s a federal cnme

484 Chapter 12 Chemistry of Some Hazardous Organic Compounds: Part r

r\·ers 10 exerci se caution. Line markers d . . 0

~ ' ipd ine, nor do they provide the pressure :f~~: mdicate the exa~t la:cat ion ?r d_epth of ih Pl ine markers arc posit ioned as fo llows: natural gas movmg m the p1pelme,

• The line marker for aboveground i 1· • S((llon 3cce~si blc to the public. p pe mes is placed and maintained along each

The hnc marker fo r underground pi r · 1 . . roJd, ra ilroad, and waterway crossings. pe mes 15 Paced m nght-of-way areas :ind at

l\amf~~~:;;~:n~:~~:~cn t~-lin:s themselves ~ y represcm hazards due ro leaks caused b)' narur:i

1 . ' Y . iggmg and excavauon, surface corrosion, and other 1rou-

bl C-S• In ihc U~1ted States, ap~roximacely half of them, 250,000 miles (402 000 km) are steel Of casr-ir~:a~~~/~~~c~::~

111 ::~il~~d~,~ore 1~70. Pri_or to their_ installation, chcy

1 wer_e not

generally . P ,1th anticorros1on protemon, nor were they equipped ,rith auwmattc shut-off valves. Consequently, when they rupture, the release of narural gas ofttn must be stopped manually. Because many pipelines 1hat were installed four and five d"'-1des ago _no~ arc badly corr?d~d, they could rupture catastrophically at an)' 1ime.

These pipelines resembl~ t~ckm~ ti~e bombs, as noted during the past decade when ruptured natura l•gas-transmission pipelines released massive fireba lls resembling BLEVEs (Stction 3.8-A)._ In ~010, for example, the rup1ure of a segment of a 30-inch•diameter pipelin~ i_n a resi?enrial area ~f ~an Biuno, California caused the release of approximate!)' 47,6 m1!11on cubic fee t.(1.4 million m l of natura l gas 101he environment.' The gas ignited and burned for 95 nunutes before a public utility employee could operate the manual vah·es 1ha1 stopped the gas flow. The pipeline segment had been ins1alled in 1956 and nearb)' segments had been insta lled in 1948. The fi re caused eight fata lities and num;rous injuries as well as the destruction of 38 homes and heavy damage to another 70 homes. Emergency responders cou ld only attack the secondary fi res ignited by the blaze.

The rupturing of a main transmission pipeline is not the sole hazard associa1ed with ddi\·ering natural gas to the spot where it is needed. Before it is distributed 10 furnaces and appliances within buildings, natural gas first mea nders within pipelines that were placed through shafts and ceilings, under floors, and around gas boilers. When the pipe- lines dcmiorate, crack , or are otherwise damaged, narnral gas leaks from them into the 5Llrrounding environment, where it ma)' accumulate and pose the risk of fire and explo- sion. The detection of 1hese leaks is the responsibility of the local gas utility company, but firefighters usuall y are asked to assist in accessing areas and preventi ng explosions.

Lea king natural gas may be initially identified by its odor, a hissing or roaring sound, discolored vegetation surrounding the pipeline, or wa1er or dirt blowing into the ai r. However, when leaks of natural gas originate from buried pipes, the odorant may adsorb 10 particulates of the surrounding soils. Consequently, odor alone should never be used to determine the source or intensity of natural gas leaks.

A more practical method for detecting natural gas leaks involves 1he use of monitors 1hat c.in be aimed at a buried pipeline ro detect a natural gas leak or assess where a buried pipeline was accidentally damaged during an excavarion operarion. To detect the location of t~e leaks, emergency responders aim them from a safe distance within buildings at suspect areas hke holes or vents monitor the methane concentration, and assess whether the area may be safely accessed.

Na;ural-gas-distribution pipelines appear to be buried al~o~t evel)'\vhere in residen- tial areas, nor just beneath 1he surface of streets an? al_leys. F1rcf1ghter_s often accompany gas company employees to scenes at which these ptpdme~ have been_ madverrently dam- aged during a routine landscaping or other soil•excavau_on operauon. Da~age to the pipeline may cause a natural gas leak that has the potem.ial to produce service outages, evacuations, ignition, property da mage, injur)', or loss of life.

·P1pdme Accidenr Report ~sJn Bruno, California, Narural Gas Pipeline Explosi~n and Fire, Septe~bcr 9, 2010,~ NTSB No. PAR-I !-0 I, PBzot l-916501 {Washington, DC: Narional Transpon.11LOn Safety Board, _QI I).

Chapter 12 Chemistry of Some Hazardous Organic Compounds: Part I 485

I I

/I I

I

I ! 1

1 I

I I

II ///

/1

To r~uce or dimin:ire the occu~rence of such incidents, local gas cornpanies and 1 ordinances often require the fo llowing: OcaJ

Contact the local g3s company befo re staning 10 excavate. W:iit until a tr:J.ined cechnici:rn fro m the company has flagged the location of the line (usually within less rh:m 24 hour~). P1 Pt. Mai ntain tht' pipeline m:uks and avo1d.1heJlagg_ed areas when excavating. Contact the company again if 1he pipeline is acc1~entally damaged during

311 ex

tion operation 50 that che dam:ige can be profess1?n_ally as~essed. Even a tnino/a1•a- or scr:iping of the pipeline may cause future leaks tf It rem,uns unrepaircd. d~nt

A narurnl gas pipeline ma y be loc:ued near a sewer line. Whe1~ the pipeline is aged, 3 leak of natural gas may percolate through th~ ~ubsurface sod and enter the :~- sysrcm. Then, bubbles of natural gas arc obser\'ed mmg through standing Water on ~Cr surfuce or even in toiler bowls. Th~ odor of natural. gas may als~ be detected when Usi!e a rooter device ro clear an obstrucuon or blockage m the sewer line. g

When a natural gas /e::ik is ~ppa rent or s_uspccted. anywhere, gas companies recolll- mend rhar indi\' iduals comply w1th the fo llowing practices:

Leave the ::irea immedia1ely by foot and leave the doors open. Do nor light a march, start or srop an engine, .u~e a telephone, turn light switches or appliances on or off, or perform any other act1v1ty tha t may generate a spa rk. Warn others to sray away from the scene. Contact 91 J or the gas company from a distance of at least 1000 feet (300 m) from the leak. Do nor ammpr ro extinguish a natural gas fi re, but ca ll the fire depanmenc. Do nor arrempt to opera te pipeline valves.

Gas companies also recommend that residents and workers know the location of tht incoming natural gas shutoff valves into rheir homes and other bui ldings so this inforllt.1- tion can be rapidly conveyed ro firs t-on-the-scene responders when necessary.

12.5-E BULK SOURCES OF METHANE compr@s~ natural gas Aside from its transference by pipeline, natural gas is also transported as compressed (CNG) • Methane as a natural gas, or CNG, and the cryogenic fluid ca ll ed liquefied natural gas, or LNG.

liq ue fi PdnattJra l gas

cryogenic liquid

comprened gas Compressed natural gas is an alternative motor fuel whose use to power American motor vehicles has been strongly encouraged since at least the mid-2000s. When com- pared ro motor gasoline, CNG is a desirable \'ehicular fuel, nor only because its com- bustion provides a high hea r value but because fewer volatile organic compounds (Figure 7.J-J ) are components of rhe vehicle 's exhaust. Given this positive environmen- tal outlook, compressed natural gas has been chosen by severa l America n municipali- ries fo r fueling an entire fleer of buses, raxi cabs, refuse trucks, and other city-owned vehicles. Businesses, too, like United Parcel Service, use CNG instead of diesel oil to power rh eir su rface vehicles. When vehicles are powered wi th CNG, the fuel is stmd in cylinders located in the trunk area, under the side panel of a va n or school bus, on the frame, or in rhe bed of a truck. . During rhe first decade of the rwemy-firsr century, it first became popular ro transport

liquefied narural gas over long distances in large, cylindrical ra nks on speciall y construcwl refrigerated ships. Transporting LNG is more cost-effecri ve compared ro transporting CNG. As noted ea rlier in Table 2.10, when methane is cooled ro -258°F (-161°CJ, tht liquid volume is reduced ro 11650th of its gaseous volu me. By cooling natu ra l gas to 3 temper:ru~e equa l to or less rhan this value, the gas is converted into LNG.

LN.G is no_w transp~rted from foreign plants in Nigeria , Trin idad, and Tobago IO domemc pons rn the Urnted Stares. Ir then is transported on land by mea ns o( refrigrrated

486 Chapter 12 Chemistry of Some Hazardous Organic Compounds: Part 1

k irucks, del ivered ~o r~gasification terminals wh . . _ iJrl d as [he gas by p1pchne to its destin::it' 1 . ere rt ts convened to CNG, or crans-insula.red ranks. ion. t is ::i lso stored until needed in double-

When shippers transfer CNG by pipeline able gases) br any means, DOT requires a;:; ~a;ion C;'\JG o r LN? (or othc.r flam-

addition of ethyl mercaptan, thiophane, or amyi ~e·rf};::25 tha t it be odomed by

Eth)I mcn:~ptan ( l ,2-Eth.:ln<l uhiolJ

?M1-7H2 Cl·h CH, "-/ .

Thioptunc CTcu-ahydroth1or~ncl An1) l mercap1ao

(Pcnune1h10IJ

These sulfurous 0.rg:inic compounds ha ve such offensive odors that their detection is help- ful when attempting to locale gas leaks.

A.t 16 C.F.R. S306.ll, the U.S. Federal Trade Commission requires retail disrribuwrs 103ff1x a black-and-orange label that resembles the following on CNG dispensers:

MINIMUM 90%

METHANE

This label identifies compre~sed natural g::is as the alternative mowr fuel and provides the minimum methane fuel raung as 90% by volu me. The commission also requires new- \'chide manufacturers and used-vehicle dealers to affix the label on a visible surface of each vehicle powered by CNG.

12,6 LIQUEFIED PETROLEUM GAS Most people are first introduced to propane or n-butane as the substances used to fuel a backya rd barbeque grill. As noted ea rlier, propane and n-butane are alkanes having the chemical formu las C3Hs and C4H 10, respectively. The liquid mixture of these simple hydrocarbons is called liquefied petroleum gas, or LPG. Although largely produced as a fuel, its constituents also are used as propellants in aerosol ca ns.

There are three types of LPG: a propane/butane mixture, commercial propane, and commercia l butane. The propane/butane mixture consists of approximately 60% propane and 40% butane by volume; commercia l propane is approximately 92% propane; and commercia l butane is approximately 85% 11-butane. Although the main constituents of LPG arc propane and n-burane, sma ll amounts of ethane, cthene, propene, butene, isobu- 1ane, isobutene, and isopentene also may be present. For commercial use, LPG is generally isola ted as a by- product from the rectifiers used for treating natural gas.

At most ambient conditions, propane and n-butane are colorless, odorless, and tasteless gases, bur DOT and OSHA require the addition of an odorant to each type so that leaks may be easily detected. Additional phrsical properties of propane and n-butane are noted in Table 12.7. These data show that when propane and n-butane burn, they evolve af amount of heat rnnging from 2550 Btu!&' (101 ,000 kjlm3) to 3200 Btu/&' (133,000 kJ/m ). Conse· quentJy they are highly desirable as domestic and industria l fuels.

Th; data in Table 12.7 also show that propane and n-burane readily liquefy under modera1e pressure. Hence, when pressurized in steel cylinders, each of the three ~ypes of LPG exists as a liquefied compressed gas. These data also sho"".' t~at_ 11-burane liquefies near the freezing point of water. Consequently, i1s use

0 as a fue l 1s ltm1ted when the tern•

perature of the surroundings is colder than 31 °F (-0.5 C).

liquefled petroleum

three compressed commercial products consisting of a mixture of liquefied propane and butane

LPG

Chapter 12 Chemistry of Some Hazardous Organic Compounds: Part I 487

r Md,iiifMM!Mi4\G,Hi:14i:i#hbi~ PROPANE fl•BIJTA.NE -30S"F(-187"Q

~M~,tu~o~g~poE'"~'=~~~~;;=======t~--4~9•~,(~--4~5'~C)c========~~-t"t6"F(-13a,q ~oiling point ll ' F (-O.s•q Spec1ficgravityat68"F(20' C) O.SB 0.6Q

Vapordensity(air = 1) l ,52 2.04

:_:Fl•::•h~po::i":::'--,---------t,;;-l;;;S6~•F,,(-;ol;,;-04'C) _ _ _ _ T";_;::,76'F(-&o-q Autoignit ion point 874"F (468"0 761'F (40s•o Lower flammable limit 2·2" by volume 1.9¾ by volurn, Upper flammable limit 9.5% by volume 8,5% by volun,, Heat of combustion 25S0Btu/tt' 3200Btutftl l32"F (O"Q and 1 atmJ (lOl,OOO kJ/m 3) (133,00o kJlrn~

LPG and its constituents pose a health hazard as an asphyxiam (Section 10

J-A Individuals who inhale them for a prolonged period lose ~onscio~sness because th;y a!~ denied sufficient oxygen. Prolong7d exposure to LPG or either of its constituents P0Sts a potentia l threa t to life by suffocation.

SOLVED EXERCISE 12.5

bottled gas•Broadly, any gai stored under pressure in a portable gas cylinder, but more speclficalJy, propane, butane, ora propane/ butane mixture stored under pressure in a portable gas cylinder

wtry 1s propane generally mo,e iuitab1e than butane for fueling mobile appliances and heaters during very told weather7

Solution: Jt1s thegasteus state of a fuel tha11gn11tsand burns The data m Table 12 7 1nd1catethat propal'l!~i gas at temperatur~ equal to or greater than -49°F {-45°( ), whereas butane 1s a gas at temperaturtS equal

10 er

greater than 31°!={- 0 s•o These facts severely !1m1t the use of butane as a fuel rn cold climates because 1t/ffllL'll hquJd There are few areas of the wci1d where ttmperatures colder than -49°F (-45°() are expenenced; c~ quently, propanegenerallyismoresuitablethan butane forfuehng mobileapp/1ancesandheaters

12.6,A BOTTLED GAS The commercial types of LPG usually are shipped under pressure by motor or rail tankcar from peuoleum gas wells and refineries to filling stations, where they are transferred into a bulk storage tank. Distributors then transfer them into horizontal or vertical dispensers from which they are further dispensed into far smaller portable, thick-walled cylinder; and tanks. The contents then are said to be "bottled" and the gas is commonly referred to as bottled gas. The gas cylinders and tanks are convenient to deliver to rural areas ~nd ocher locations where natural gas cannot be supplied economically by pipeline. They art always stored outdoors, because local codes and ordinances prohibit indoor storage.

Ca re muse be exercised in storing porrable LPG tanks. When it is rapidly subjected to incense heat, they can rupture. The rank may also be struck by lightning or be exposed ro another ignirion source. In these instances, the rank contents immediately ignite as a fire- ball as they expand into the atmosphere.

LPG is also transported by 1ruck to fill permanently installed tanks. These ranks are always situated ar prescribed distances from homes and other major buildings and con· nected by means of copper tubing to appliances and furnaces loca1ed indoors. .

The largest volumes of LPG are found at LPG-fi lling stations, which arc loca_re~ in virtuall y every major city. Ar these fi lling stations, the LPG genera ll y is contained within ~ bulk storage tank having a maximum capacity of less rhan 90,000 gallons (340 m3).

488 Chapter 12 Chemistry of Some Hazardous Organic Compounds: Part 1

12_6.e LPG AS AN ALTERNATIVE MOTOR FUEL G c.in also be usC'd as an altC'rnativC' motor fu I

1 .

t~iurrd as the world's fi rst LPG.fuC' led car. t" • n l008, Hyundai's Eltmtra was manu- At 16 C.F.R. S306. l2, the U.S. Fedrral Trade Co ..

coaffLx orange-and-black labels on their LPG dispense:~:~:~u~~:,~:'~-~~t~'.~t~~;~:ors

MINIMUM 90%

PROPANE MINIMUM

90% PROPANE 2% BUTANE

Tht~e labds identify the' a_lternative m~tor fuel as liquefied petroleum gas and provide the rni n1mum perce~tage 6> ,olume as 90¼ propane (on the left ) and 90% propane and 2% buiane (on the nght ). T~e U.S. Federal Trade Commission also requires new-vehicle man- ufacturers and used-vehicle dealers to affix the label on a visible surface of each vehicle ihar is powered by LPG.

~ at s~1al actions should foef1ghtei-s implement when r~pond1ng to the SCffie of a car crash rnvotv1ng a LPG-,~:ed l'th1cle?

Solution: Once the vehicle has been slilb1hzed and secured aga nrt movemfflt, f1rdightm should f1m a'.>Certam t>iatrt 1spoweredby lPG Thenatureof thevehicular futl mayberead1lyiden11fiedbylocat1ngthelabelaffaed to the ve hicle Having determined that the vehicular fuel 1s LPG, fim-on-the-scene re~nder; should then tum U1egas cy11nder valvehandle tothe "oft• postt10n and~archfOfs1gnsoffutlleakmgfromrupturedconneC11on fttngs andhnes. F1ref19hter;shouide)(ljngu1snallnearby firesandremoveaUpotent1alsourcesofheat The use offlaresshouldbeavo1dE'dalthoughnonsparkingmarbr;orconesmaybeusedtocordonoffahazardzone 1,1os1 1mportantl~. firefighters should bear m mmd that when LPG cyl,nders are exl)OS@d to 1nteme heat, they wlll r11 Pture and catastrophically releasE' th!'1r contents to W ffi..,ronment as a BLEVE (Sectlon 3 8-Al This s1tua11on snouldbeavoidedatallcosts

Ethylene Propylene

12.7 ETHYLENE AND PROPYLENE Ethylene and propylene, or erhene and propene, respectively, arc 1he common names of the simplest alkenes. As noted earlier, their chemical _formulas a~e CzH4, or CH2=CHi, and C3H6, or CJ-1 3- CH=Cl-11, respectively. The physica l ~rop_em_es of ethylene and pro- pylene are provided in Table 12.8. The tabulated infor~atton m~1ca~es that ethyl.en~ and prop)•lene pose the ri sk of fire and explosion when either gas 1s discharged within an enclosed area, . h II

Ethylene and propylene are produced in the United St~tes 1~ larger amoum 1 s t an a f

. I . d h e used primarily for the manu acture o other subsrnnces. In the chem1ca 10 u.Stry, t ey d 14 6

_ 8 ·) b t they are also used as

polyethyle~e and polypropylene (Semons .14.6-f ~~er ch.emic~l ~rodum . raw materials fo r the manu fac~ure of a van~ryl :nJust . For example, in the agricultural

Ethylene is also used outside the chemtca . ry field, it is used as both a plant regulator and an herbicidr: . .

I b hastening the uniform npen mg of apples,

i I Ethylene performs as a plant re~u at~r .Y . h siimulation of seed germination and

bananas, berries, figs, tomatoes, and Citrus ruits, t e d Organic Compounds: Part I Chapter 12 Chemistry of Some Hazar ous 489

1.3·Butadiene

MhiiiA=IMi&SWU:44\.tl-i§ ;~ ITHYLENE ~ YLENE ·

Meltingpoint -272"F(-169"C) , -30~ ( -ies•o - 1ss"F <-104"Cl _54.F l-1s•o

Boiling point

Specificgravityat68' F(20"C)

Vapor density (air "' 1)

Flashpoint

Autoignition point

Lower flammable limit

Upper flammable limit

Heatofcomburtion [32"F WO and 1 atmJ

0.001 o.s, 1.0

-2 l3"F (- 135'0

842"F(4SO' C)

3.1 % by volume

32% by volume

21 ,600Btu/lb (50,JOO kJ/kg)

sprouting; the curing of robacco leaves; the_ production of flowers in pineapples; and the normal thinning of flowers, leaves, and frun from trees as they mature.

Ethylene performs as an herbicide by controlling the spread of wirchweed in corn, cotton, peanut, and soybean fields.

Ethylene and propylene can pose health hazards as asphyxiams, Individuals who inhale either gas for a prolonged period lose consciousness because rhey are denied sufficient oxygen Prolonged exposure ro these gases poses a potential threa t ro life by suffocation.

12.8 BUTADIENE l ,3·Buradiene is a colorless, highly fla mmable gas wirh a mild gasoline•like odor. Its phys• ical properties are provided in Table 12.9. The gas often is manufactured ar petroleum refineries by rhe dehydrogenation of l·burene and 2·burene.

CH, CH,CH =CH,(g) - CH2= CH - CH = CH,ig) + H,(g) 1-BUl)nt

CH3CH2=CHCH3(g) - CH2= CH- CH = CH,ig) + H1(gJ 1-Hut~ ne

I .J -Bul:tdiene

l, l-Hu1ad1me

1-l)Jrogcn

H)drogcn

Md=l!ifii Physical Properties of 1,3-Butadiene Melting point Boiling point

- 164°F (-109"C)

Specificgravity at 68"F(20°q 23'f (-4 .7' ()

1.88 Vapordensity(air: 1) Flashpoint

1.97

Autoignition point -105'F(-76'C)

Lower flammable limit 804"f (429' ()

Upper flammable limit 2% by volume

11.5% by volume

490 Chapter 12 Chemistry of Some Hazardous Organic Compounds: Part I

J-But;id iene is 3 \'Cry reactive substance h I,! for molecule, to fo rm pol)'buradiene ·(S e~en reacts Spontan eously with itself, mole-

;~>eis mixed \\'. ith ;in inhibitor during its pro~:~~i~~ 4· 11 ·B). To prevent the reaction, the Conunerc1ally, the product is ca lled but d' · .

11 often is transferred from production planr: b;n;~:~~:~ut. use_ of the numerical prefixe~. cal pbnts where the gas is used to manufacture va ri P1~elines to nearb_y petrochem1- auiomobilc 1ir~s, a~pl ia nce pans, pipes, and synthetic ~:r1; pes of S)'ntheuc rubbers fo r

I J-Bu1ad1ene 1s produced as a product of h • · prod~m, wood, and tobacco. Individuals who 1\,: ~~':,mp;'." combusti~n of. proleum i1•hkh butadie_ne is produced or ~sed are more likely ~ha~nt~: ~:anre~:I ustn: laat~:ans ;: brea1he butadicne. B_eca.u~e butadiene is formed during the incomplete ::bustion of petroleum ~roducts, individuals who routinely breathe 1•ehicular exhaust are also at risk of contracting can_cer. In the '-:0 rkplace, OSHA requires employers to limit emplorce exposure tokad maximum butad1ene concentration of I pan per million, al'eraged O\'er an 8-hourwor ay.

When individua ls breathe 1,3-butadiene, thev experience nausea ere nose and throat irritation, h.eada~he, and decre~sed blood pre.ssure and pulse rate. Long:term ; xpo- >ure to 1,3-but:diene increases the r_1sk of .com~acting stomach, blood, and lymphatic- srs1em cancers. Based on these studies, ep1dem1ologists rank 1,3-butadiene as a human carcinogen.

Beca use 1,3-butadiene is one of several carcinogens formed during the incomplete combustion of tobacco,

9 smokers are exposed to 1,3-butadiene when they inhale tobacco

smoke. Beca use it is highly reactive, scientists beiie1·e that the substance poses by far a more significant cancer risk to smokers and individuals exposed to secondhand smoke compared to the other carcinogenic components of tobacco smoke.

12.9 ACETYLENE Acetylene is the simplest alkyne and the sole member of this class of compounds that has commercial importance. As noted earlier, its chemical formula is C2,H

11 or H-0:=C-H.

The physical properties of acerylene are pro\'ided in Table 12.10.

ifrjjjij/,; Physical Properties of Acetylene Me lting point Soiling po int

Specif ic gravity at 68"F(20"C) Vapor density (air= 1) Flashpoint Autoignition point Lower flammable limit Upper flammable limit Heat of combustion [32"F (0°C) and 1 atmJ

Sublimes - 118'F{-83°C) 0.91 0.899 O' F(-18°() 635' F(335"C) 3%byvolume 82%byvolume 12018tu!ft3 (49,900kJ/m3)

IN. Sarhiakumar et al., ~Mortality from cancer and other causes of dea1h among syn1hc1ic rubbtr workers/

fcmp. bwiro11• Med., Vol. 55 (1998),pp. 230-Z!:;kt C.Ot1~$ DiseJu: Tl,e Biology arrd Btli~l'i~ral Bas is ~:

Acetylene

Repon of th~ Surgeon Gener3l, Horii TobaccoD~scase Control and Pm·enrion, Atlama, Georgll (_0\0) (ISB. S111okmg-A11, ib 11tab/e Distase, U.S. Centers for

IJ: 978-0- 16-084078-4). . f 5 e Hazardous Organic Compounds: Part I Chapter 12 Chemistry o om 491

I I I""

7

I 'I I _,_

I I I

dehydrogenation • A chemical process typically conducted at a h igh temperature and pressure and during which molecular hydrogen is removed from a compound

In the United States, acerylene is produced mamly by cracking natural gas.

~C H..i(g ) - C2H 2(g) -,.. -~H i (g) ACtl ) kne

In this instance, the cracking involves dehydrogenation. Although pure acct ·le . colorless gas with an etherea l odor, industrial-grade acetylene can be fo ul-s > 1/e 1s a noted in Section 9.7-8, industrial-grade acetylene sometimes is produced by ~Tl~ ing. As ca lcium carbide. Because calcium carbide generally is contamina1ed with ca]~ rolyzing ph.ide, the foul-smelling phosphine is simultaneously produced. ciurn Ph0s- . Acetylene is an _innarely unstable substa.nce, decomposing a~ a n explosive ra te i ;~

0 ~1:;:;.cs when 1r has been compressed m excess of approx1macely 2 atmosphe::

The decomposition is especially likely when the comp ressed acetylene has been sub· d to thermal o r mechanical shock. Jecte

Nor only is acetylene flammable and innatel y unstable, but it a lso reacts with c . pounds containing the copper(!) ion, especially in moi st air. The product of this chem~~ reaction is copper(I) acetylide, which when dry, can decompose explosively.

H -C:= C - H(g) + Cu * (s) - H -C=C -Cu(s) + H ~(aq) Acct)kne Copper(I J1on Coppcr(l) ;Kclyhdc Hy<lrogcn 1on

To reduce or eliminate the po1 en tial for this explosive reaction, welders and other indi- viduals who work with acetylene avoid using copper fittings or tubing on arnrlene cy linders.

When spa rked , a mixture of acetylene and oxygen burns with an intensely hot name, reaching temperatures as high as 5400°F (2982°C), This combustion proms yields 21 ,400 Btu/lb (49.9 kJ/g), which is put to use when we lding and cutting steel and cladding meta ls.

Careless welding practices have caused many major fires. Heat that is sufficient to weld steel is capable of triggering the ignition of many other commonly encoummd f1ammable materials. When acetylene is used to generate heat fo r welding, the risk that its hea r of combustion will be transmitted to nearby f1ammable materials should alwap be acknowledged.

To counteract its potential decomposition, a special method is employed co safd)' compress. ~nd store acetylene within steel cylinders. Thi s procedure rakes advantage of the solub1hty of acetylene in acetone. One volume of acetone dissolves approxim;m\y 25 volumes of acety lene at 1 atmosphere (101.3 kPa ) and 300 volumes at 12 atmos· pheres ( 1216 kPa ). By di ssolvi ng acetylene in acetone, gas manufacturers increase ihe amoun~ th~c may be safely compressed in cylinders by means of the three-step p~ocess sho~\'n 111 Figure 12.5. First, they pack the cylinders with a porous medium consisnng_of 3_ m~xture of mo_nolithic fille r and ba ls3 wood. Then , they satu rate this mediu~ wi th

liquid ~ce~one. Fi ~ally, they charge acetylene at a presc ribed pressure into the cyhnders. ~v here 11 di~solves m the acetone. As acetone solutions, acetylene typically is compret~ m sreel ~y lmders of various sizes whose volumes range from 9.9 cubic feet (0.28 m )t 390 cubic feet ( 11.04 ml) .

Acetylene poses_ a health hazard as an asphyxianr. Indi vid uals who inhale acecykr fur a prolon~ed .period lose consciousness because they a re denied sufficient oxyg~n ir, :1L~:r:::lti:~:1rat1on. Prolonged exposure to the gas poses a potenri:d threat to hft }

492 Chapter 12 Chemistry of Some Hazardous Organic Compounds: Part 1

Removable metal cap

Acetylene capacity appro1uma1ely - 275 ft3 at 250 PSI - _ - and70•F - _ (21 "C) ~- _ _ _

°§§

12!j3115~} ~er11~dlametsl'_

FIGURE 12.5 Th1~cut• awayof an acetytene cyl- •nder 1l\umate\ 1ts unique lea:ures Themonolith,c Mlerorbalsawood 1sa porous materi al that is chargedw1lhacetone. into which the acetylene subsequently d,~!>Olvu

Monolithic filler or balsa wood

12.10 TRANSPORTING THE SIMPLE GASEOUS HYDROCARBONS

When shippers offer acetylene, butadiene, ethylene, methane, or propylene for transportation, DOT requires them to identify 1he chemical commodity as shown in Table 12.11 on an accompanying shipping paper. All labeling, marking, and placarding requirements apply.

illliifiii HYDROCARBON

Acetylene

Butadiene

Butane

Ethylene

liquefied petroleum gas

Methane, compressed

Methane, cryogen ic Propane

Propylene

Shipping 0e'.icnpt1ons of the Simple Gaseou'.i Hydrocarbons

SHIPPING DESCRIPTION

UN1001 , Acetylene, dissolved, 2.1

UN1010, Butad!ene, stabil ized, 2.1

UN1011. Butane, 2.1

UN1962, Ethylene,2.1 UN1075, Petroleum gases liquefied, 2.l o, UNl075, Liquefied petroleum gas, 2.1

UNl971, Methane, compressed, 2.1

UNlgn, Methane. refr igerated liquid, 2.1

UN1978, Propane, 2.1

UN1077, Propylene, 2.1

Chapter 12 Chemistry of Some Hazardous Organic Compounds: Part I 493

494

DOT also requi res the issuance of a ha za rdous i:naterials sa fety permit (Section t tor carriers before they transport methane as either a compressed gas or

3 . 6.101

1~: ~ wi,h , me<hane con<em of at krn 85% in bulk packaging ha,ing a capa~,~~••e to or gre;iterth:m 3500 gallons (13,248 L). . . . qU,al

When LPG is transporr~d in a DOT Specification_ M _330 or 33 J tank truck, Do requires ca rriers ro d~tm~me wher_her. the com~o?uy 1s corrosive and 10 indicate thT appropriate information m the shtppmg ~esmp110~ _as ~n .. e of the _following: "RQ• UN I075 Liqudied petroleum gas, 2.1 , (Non-corrome), RQ, UNI075 Pe,

1 ,

ga~, liq~efied, 2.1 (Noncor)," or "RQ, UN1075, Liquefie_d petroleum gas, i.. 1 (~::~l!J

Q and T ranks)." Noncorrosive LPG may be transported m tank trucks thac hav constructed from a special steel that is "quenched and tempered," or "Q and T." e

When a Oammable gas is transported in bulk by highwa y or rail, its name m br displayed on two opposing sides of the rankcar used fo r shipment. When it is transt by rail in a DOT-113 rankcar, DOT requires their carriers to di splay FLAMMABLEo~~ placards on squares having a white background and black border. S

When shippers offer nonbulk ~uantities of unodorized LPG fo r transponarion, DOT requires them to mark the packaging NON-ODORIZED or NOT ODORJZED near th spot where the proper shipping name is marked. e

12.11 AROMATIC HYDROCARBONS The word aromatic suggests that aromatic hydrocarbons are compounds possessing fragrant odors. The odors of some simple aromatic hydrocarbons actually are fragra nt bur otherwise, this perception is misleading. Aromatic hydrocarbons are regarded ,; compounds whose molecules are composed of one or more special rings of carbon a1oms. These compounds are typified by the substance ca ll ed benzene, the simplrn aromatic hydrocarbon. Its chemical formula is C6H6. Although the molecular structure ~f benz~ne ~a )'. be represented by either hexagon shown on the left in the following illustrauon, u 1s more commonly represented by a hexagon wit h a circle inside, as shown on rhe right:

00 0 Aromatic and aliphatic hydrocarbons thus are differentiated by rhe fact that rhe

~olecular struc~ures of aromatic hydrocarbons have one or more hexagonal benzrne nngs, usually with side chains, while the molecular structu res of a liphatic hydrocarbom do not. Hereafter, the molecular structure of benzene wi ll be represented by the hexagonal st

ructural formula with the inscribed circle. Ir is called the benzene ring. Although thr symbols of

th e carbon atoms are nor written as part of the hexagon it is always under· st

fd th

ac a carbon atom occupies each corner of the hexagon wher; i1 is bonded to rwo ot er carbon atoms and a hydrogen atom. '

Wh~n any one of the six hydrogen atoms in benzene is substituted with a methJ"I rh:"!t~'.,:T;:;~~~t ;;:~i"'"I'.' is called methylbenzene, or more commonly, roloe~ as follows: uene is C61 l s-CH3, and its molecular structure 1s represent

o-CH, When two hydrogen atoms in th b h I upl,

the resulting compound h h h e . enzene molecule arc substituted with met r position the methyl grou;: itn ~~re:m~~:r formu la C6H.1-(Cl-!3b Bec?use it is poss1~1:r~~

Ch . 1 fercm ways on the benzene nng, three mu apter 12 Chemistry of Some Hazardous Organic Compounds: Part I

6-· ·6 .6 6-. ¢ onho B

isomers for the formula C6!---Li-(CH3)i exist. These three compounds are the struc1ural iso- mers of dimethylbenzene, or xylene. Their molecular structures are written as follows:

OCH, l .2-0111ic lh ) lbi:n1cn~

\o- X)lcnc) !.J-Dn!lelh) lt-enun~

(m•X)kllC)

¢ CH,

l ,-l-D1n1c1h)!lll:n1.cnc IJ>·X)lcnc)

In the common system of nomenclature, the prefixes ortho- (o-) , meta- (m-) and para- (p-) are employed to identify disubstituted benzenes. Ortl,o- means "str~ight 3head," meta- means "beyond," rind para- means "opposite." In commerce, the isomeric mixtures of xylene arc sometimes referred to as either .. xylene" or "xylene(s)" with total disregard for their isomeric distinctions.

The simplest dcri\'atives of an aromatic hydrocarbon are compounds in which a sin- gle alkyl substituem has replaced a hydrogen atom on the benzene ring. These compounds are named by identifying the substituem followed by the word "benzene." For example, the compounds having the fo llowing molecular structures are named ethylbenzene and 11-propylbenzene, respectively.

Eth) lbcnmll:

O CH,CH,CH3 n- l"rop) lben~<' nc

When two substituenrs have replaced two hydrogen atoms, their loca tions on the benzene ring must be identified. The molecular structures of the three compounds in Fig- ure 12.6 illustrate two arbitrary substituents, A and B, positioned on the benzene ring. B is located in the ortho-, meta-, and para- positions relative to the position of A. When naming the disubstituted benzenes, 1he italicized letters o-, m-, and p- are used as prefixes to identify 1he location of one substituent relative to the other one. When one of the two substituenrs is a methyl group, the compound often is named as a derivative of toluene as 1hown br the following examples:

p•Elh) ltolutn~ o•hobUl}l!olucnc

ortho- (o-), meta- (m•).

prefixes used to name disubnituted benzenes inthefollowing man- ner: ortho-referstothe subnitution of the hydrogen atoms bonded to adjacent (the first and second) carbon atoms on the benzenering;meta- referstotheir subnitu- tion on the first and third carbon atoms; and para-refers to their substitution on the first and fourth car- bon atoms

Chapter 12 Chemistry of Some Hazardous Organic Compounds: Part I 495

t1 1 11

l:1

des,gn.i tion for the benzene rmg when 1t b; namedasasubrutuent on another molecule (C.,H~-l

d6ignationforthe seven-carbon atom unit coruittingofcombined phenyl methylene groups (Ci;H5CH2- J

aryl group {aryl

the phenyl or benzyl group of atoms. obtained by removing a hydrogen atom from thechemiu t formulas of benzene and tolu- ene, i.e ., C.H,- and 4 HsCHz-, respectively

BTX The collective name given to ben- zene.toluene, and the xylene Isomers

illiiifiN

In the IVPAC srstcrn, when rwo or more alk)·I groups arc bonded to the rhe resulrmg hydrocarbon 1s named by hsrmg the al kyl groups alphabcucally mg the first group with a I . Each of 1hi: six ca rbon atoms in the benzene ruig bered from t 10 6. Two exampli:s that illustrate the use of this rule for deriv:rn,·es of aromatic hydrocarbons are shown next:

I-Bh)l•2 nprup) lbcnLtnc I bol'll!}I l ,, prup) lbcM~n~

Aromat ic hydroca rbons sometimes arc named by ident ifyi ng th e C H C6 H;CHr groups of aiom:;. Cb! I;- and C6H5CI Ir arc called the phenyl :nd benzyl group, respectively. They are examples of aryl groups, or aryl substituents. nd

-0 -CH,-0 A~n, }I group

Thus, the compounds having the following molecular s1rucrures are named phen}·lrth 1 ene and dibenzylacerylene, respecti1·ely. ) ·

01 tx-n,} llCcl)l~,1,:

12.11-A BENZENE, TOLUENE, AND XYLENE(S) Benzene, toluene, and xylene are the three mos! commonly encountered aromatic h)·dro- carbons. They arc sometimes referred to collectively by the acronym BTX, Benzene, to]u. ene, and xylene(s) are colorless, water-insoluble, highly 1•olacile liquids. Some importam ph)•sical properties of benzene, toluene, and xylene{s) are provided in Table 12.12. Their

Physical Properties of Benzene, Toluene, and the lsomem Xylenes

BENZENE TOLUENE / o-XYLENE m•XYLENE I p-XYLENE Meltingpo,nt 41 ' F(S4"C) j -139' F(-95' C) ( -15' F(-26' C) - 54"F(-48' C) 55' F(13' C) _,,_m~,,~po_;_"'-----i-c.:.:l116"F_1s_o·c_1_~/-" _' '_F1_111 °c) / 291 'F(1 44'Cc-J-t-,-.,-.,-1,-,,-.,-1-,1-,-so--,-11"'JS:-:'O- specificgravityat68' F(20·O 0.88 / 0.87 1 0.90 0.87 ! 0.B6 Vapordensity(air= 1} -~,-;, -;;_, ----"-:-, .:-', ---lt'l:::.,::__--+3'.::_7::___ ___ l;._:l'.:.7::__ __ Vapor prern.ire at 68' F (20' 0 ' 75 mmHg I 22 mmHg 8 mmHg 8 mm Hg ) 9 mmHg Flashpoint l 2' F (- 11 ' Q ) 40' F(4.4"() / gO' F(32,C) B4' F(29,C) Bl ' F(27' Cl _

Autoignitionpoint ~ ' F(S62' 0 I 997' F(Sl6' C0 867"F(464' C) 982' F{528"C) ) 984' F(S29'Cl Lower flammable limit , 1.4¾ byvolume j 1.4%by,ol"me I.O"by,ol"me ' · " ,. " 1.1% by volume I l . l¾byvolurl'.t _Upper flammable limit 8% by volume I 6.7% by volume I 6.0% by volume 7.0% by volume I 7.0% by vo~ Evaporat lonrate. (ether= l) J_!.s ) 4.5 I 9.2 9.2 I 9.9 Heatofcombustoon 18 184Btu/lb 18200 -7 -r -- [32' F(O'C)and 1 atmj (4i300kJ/kg) {4i3ooet~'lb 18,400Btu/lb , ,8,4008tu/lb j 18,400Btulibl

• ' J/kg) (42,B00kJ/kg) (42,800kJ/kg) (42,B00kJ/kg

496 Chapter 12 Chemistry of Some Hazardous Organic Compounds: Part I

Aashpornts. flamm,1b!c ranges, and heats of combust1 l>soci:11ed with them is fire and explosion. Their comb on mdica1e 1hat the primary nsk Jucr ion of smoky ~arncs consistmg of particulate maustion 1s characterized by the pro- l"'Jynucle:1r aromatic hydrocarbons (Section ll . \2-C) a~:~r~o which the cancu-causing

Benzene, rolu.ene, and xylene are manufactured b , · c:1i:ilrnc reforman~n of alkyl cycloalkanes at hi h tc Y_se\eral procrsses mcludmg the

J chrmJCal reacuon involving the refo m g f mpcrature and pressure. Reformation ~tha substances. It .almost alwa)'S occurs rwi~~gt:c sr;;tl~cules into different molecules of

When naphtha 1s suhiccted to the conditions of c~u tan~ous loss o~ hyd.rogcn. C}·doolkanes arc converted 1mo compounds within the 8~tic uforma uon, 11.s constit~cm il!U>m1te reformation reactions that result in the production of t.:~~~~:l~~~::\:~~ :~.;~::~

Q-rn,1,1 Q,,1 + 311 ,," ~ CH1(g)

~ CH1(g) CH3

1,J.LJ ,n~ th)IC)dohruoc

lol u,: ,.._,

0-CH,lol +

CH , 11 X}kno.· ll)dmi;co

In the che~1ical industrr, P-xyle.ne is the most commercially important xylene isomer. h competes with naphthalene (Section 12. 12-A) as 1he raw material needed to manufac- ture phthalic a~ydri~e, a substance widely employed for the production of certain resins and pol}·esters mcludmg poly (ethylene 1erephthalate) (Sec1ion 14.2-B ). Table 12.12 shows that the. boiling points of m• and p-xylene are very similar. This similarity permits them- and p- isomers ro be sepa rated from 1he o• isomer. The isomeric mixture is heated to rnporize its components within two temperature ranges; then the vapors are condensed ~nd i~dependently collected, Fina.lly, the p- isomer crystallizes as a sol id, which allows its 1solmon from m-xylene by fi hratlon.

Although benzene once was a popula r industrial solvent, it is no longer widely used fo r this purpose because workers' exposure to benzene vapor caused 1hem to contract acute mrelogenous leukemia and aplastic anemia (Section 12. 11-B). Following thi s dis- covery, indust rial employers turned 10 using toluene and xylene as replacement solvents.

Notv.•ithstanding that worker exposure poses the risk of contracting cancer, the BTX group of compounds still is used by the chemical industry in substantia l quantities as a raw material for the manufacture of other organic compounds. For example, benzene is used to produce ethylbenzene and isopropylbenzene.

Q 1, 1 + CH! = CH2(g) O CH,CH3(g)

ll cn,cn~ Et h) krn., 1:Jh)lbc:nl<'hC

olg) + CH3CH= CH~(g1 O CH(CH,1,(g)

lkntc ne Pml','nc hoprop)lt'<'nune

1Cum,.-~1

chem ical react ion in which certain sub• stances art reformed intod,fferent substances.often a<companledby dehydrogenat ion

81nzen1

Tolu1n1

Chapter 12 Chemistry of Some Hazardous Organic Compounds: Part I 497

I I' ii

I

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11

1,/1 ----

Xylenefs)

.acute~logenous Jeukem J.a • Thecancer of the blood that dl!V! fops inwh1te blood cell.s. often ,mo- ci.ated with chronic v:posuretobenzene

.apl.asti t ,1neml.l • A bonemarTOw injury, often associated with v:posure to benzene

d · transported commemally in nonbulk and bulk Con~i~c;a~T:\~:1;

1

1::i~~ 0?101uene and xylene _form~rly were used as container\ sol1·e1u•b.1sed paints and other coatings, adhesives, mks, and con1emporary umes, EPA regulations h.1vc- reduced the use o

comfo1~:~; ~ 0

: 1~~~: i;:1:~~:·nal nrc-<led for the production of trinitrotoluene and tolu dusocyanare. The xylC'nc isornC'rs are valua~le constituents of motor and aviation gaso!irnc because of their high octane number~ (Section 12, 13). lbey ar.c also used in the chetni Qcs industry as feedscocks for the producuon of compounds needed m the polymer indUstry. e:aJ

12.11-B ILL EFFECTS CAUSED BY INHALING BTX VAPOR Among thC' simplC'st hydrocarbons,. bC'nzene y~ses rhe most_ serious health risk whrn I!$ vapor is inhalc-d. Short•term effects include d1zzmess, confusion, ?nd asphyx_iation . .\fore. on:r. in humans, benz~ne is a well-known hemo- and neurotox1cant; tha t is, when hen. zenC' vapor is inhaled, rt negari1·ely affe:cs the ~lood and the central ne~vous systems.

Exposure 10 benzene is also assocwted wi_th t~e potential onset m humans of fo~r types of leukemia (cancer of the blood-formmg tissues and ?rgans )_, one of which 11 acute myelogenous leukemia, a generally _fa tal cancer durmg which the ininiaturr white blood cells in the bone ma rrow rnulnply uncontrol!a bly . • \1ost blood cells arc manufacturc-d in the bone marrow. Myelogenous leukem!a usually develops after a latency period of approximately 15 y~ars. ft~ onset_ us~a_lly 1s

1 accompanied by a second

illness known as aplastic anemia, dunng wh1ch_an rndividua ~ s _bone marrow is irm-m. ibly injured. The presence of white blood cells m the blood 1s importan t, because thcst cells fight infection in the body. Consequently, even with treatment, individuals wbo have contracted benzene-induced acute ~yelogenous leukemia often are more suscepti- ble 10 infection and have a poor prognosis for full recovery.

Because benzene exposure by humans is dearly linked with the onset of cancer, ep 113(. miologists d :mify ir as a human carcinogen. EPA estimates that a lifetime exposure to 4 parts per billion benzene in air results in one additional case of leukemia in a population of 10,000 exposed individuals.

Exposure ro toluene and xylene is nor linked wi th the onset of cancer. Howem, rht inhalation of their vapors irritates the respiratory system and depresses the ccntnl nrr- 1·ous system. Initially, the inhalation of toluene and xylene vapors causes dizziness ar.d nausea, and long-cerm inha lation can have a narcotic impact on the body. The long-term inhalarion of toluene can also be addictive. This dangerous practice, colloq uially known as glue sniffing, im•olves \'Oluntarily inhaling the toluene vapor emitted by certain ~ut products like hobby glue. People who regularly practice glue sniffing risk injury to the ha, hearr,and lungs.

12.11·C WORKPLACE REGULATIONS INVOLVING THE BTX HYDROCARBONS

OSHA publishes regulations at 29 C.F. R, SS 1910. 1028 and 1910. 1000 that aim to pro· tect ;orkers fro~ exposure to ben_ze~e, toluene, and xylene. toluen;~a~le!~:::(:~Isl~~~~s\~~ limit employee exposure to airborne vapors of benzene,

• (he maximum benzene \'apor concentration has been established at I pa~t per mil· t:~~~;~:;z~::.over an 8-hour workday. This va lue reflects the cancer-causing poten·

The ~ximum tolut'ne vapor concentration has been established at 200 parts per nul· mn, a\eraged over an 8-hour workday

The maximum xylene vapor concentra;ion has been establi shed at 100 pa rts per nul· ion, averaged over an 8-hour workday,

498 Chapter 12 Chemistry of Some Hazardous Organic Compounds: Part I

iHlifiii Shipping Descnptions of Some Representative Aromatic Hydrocarbons ,AROMATIC HYDROCAR BON OR GROUPS THEREOF

senzene

~e fthylbenzene

150propylbenzene

n-P1opylbenzene

Toluene

Xy lenes

SHIPPING OESCRIPTION

UN1114, Benzene, 3, PGII

UN2049, Oiet hylbenzene, J, PG 111 (Marine Pollutant) UN117S, Ethylbenune, 3, PG 11------

UNl9 l B, lsopropylbenzene, 3, PGtll(MarinePollutantl UN2364, n-Propylbenzene, 3,PG lll (Marine Pollutant) UN1294, Toluene, J,PG II

UN1307,Xylenes,3,PG II

UN1307, Xylenes, 3, PG m

When benzene is present in the workplace, OSHA requi res employers to establish rtgulated areas where th~ c_oncemration of benzene 1·apor exceeds the permissible expo- sure limit of l part pe~ million as a ti~e-weighted average limit, or 5 parts per million as an a\·erag~ conct'nt~auo~ over a 15-mmute period. OSHA also requires employers to post the followmg warmng sign at the entrances to these regulated areas:

12.11·D TRANSPORTING AROMATIC HYDROCARBONS When shippers offer a simple- aromatic hydrocarbon or any of its dc-rivati\·es for transpor- mion, DOT requires them 10 enter the relevant shipping description on an accompanying shipping paper. Some examples for several reprcsentati\·e aromatic hydrocarbons are listed in Table 12. 13. DOT also requires shippers and ca rriers to comply with all appli- cable labeling, marking, and placa rding requiremen1s.

12.12 POLYNUCLEAR AROMATIC HYDROCARBONS There are more than 500 substances commonly called polynuclear aromatic hydrocarbons, or PAHs. The simplest members of this class of compounds are a group of structurally similar h)·droca rbons whose molecules consist of two or more mutually fused benzene rings . ~Murually fused" means that the benzene rings sha re a pair of carbon atoms and the bond between them. The PAH having rwo mutually fused benzene rings is called naphthalene. The

~··'~ "'""~ '"'•~ ·- Anthrocenc Pt>cnamhr-:nc

polynudear aromatic hydrot.1rbon (PAH)

aromatic hydro- carbon whose mole- cules have two or more mutuallyfusedben- zeneorother rings

i\Jf}hl hllrnc Chapter 12 Chemistry of Some Hazardous Organic Compounds: Part I 499

I I I

'1// 1,

~l I I I I II I ; I L 500

hettrocydicrompound

Thc- molecules of tbC' PAHs rna)' also hJl'C' four•, fi\'e- . s1_x-. or SC' \'l'n •member nn The molccu!c-s of some PAH d e r J\'3 Cl\ 'C'S consist of bc-nu nc ~mgs fused lo cycloprntc &s. (C H-) a nd other rings. The molC"cules of some PAH den va11 ves ma y cont:iin a n)I nu ro C'n or oxygt n arom (that is. J rrnrogen or OX'}'grn a tom subsrnmes for a ring C3r~ aromf. ThC' submmccs whose molecules possess one or more rmg •Homs other than car bon :m:· caJ/C"d heterocydic compounds. . . ·

All Pr\Hs are solid compounds ar_ roo~1 temperature. Although ~nd1v_1d uaJ PAI-ts ha1· bttn isobtrd and ch:i racreriu d, th t'1r mr~rures a re of co ncern pnman/y as haia rdo~c mJtl" rials. T~ey_dC"compo~e only slowly rn simpler subsrnnces; hence, once produced,

1 ~

tend ro remam m the em·1ronmrnt.

• Any compound who~ molKUh!sconu 1non, o, morermg.aroms oth~ thancarbon

N1phthalana 12.12-A NAPHTHALENE t\°aphrha!ene is the only PAH of commercial imporrancr. h is a whi1e to colorless solid generally described 35 h3ving rhe odor of mothballs. Ah hough ?.i phrh . .ilrne once Wai t/ir main constiruenr of 3 consumer produc~ u_sed as m~thb~lls,_ this spt"C1fi~ us~ is now dis. couraged. As noted m Section 12.1 J-A, 1r 1s used pri_m.:mly m the chrmical mdusrry asJ raw mareri:11 for thr m:inufacture of phth3!1c :inhydnde.

12.12-B SOURCES OF THE PAHs ,\fany processes 3ssoci.1red wuh rhe incomple_te combustion o_f organ_ic materials generate mixtures of PAHs. Hence, many manufacwnng and process mdus~nes often sptw PAHs from their smokestacks inro the air. PAHs are also dissolved consrnu_encs of coal tar and coal tar distillares, crude ~trolrum, and certain petroleum fractions mcluding heavy die- ~ , fuel , hearing oils, motor oil, heavy naphtha, and asphalt. They are also components of the emissions and residues associated wirh the burning of coa l, diesel oil, wood, wbacco and pear. They are e\·en found m minute concentrations on bread crus1s, burnr toast, and the burnt surfaces of meats cooked on barbecue grills at high temperatures.

Beca use PAHs are widely sc,m ered throughout the environment, they are frequend)' identified in samples of media collected from different sources. For examplr, the)' m idenrified as consriwenrs of lake srdiments and the particulate matter of 1obacco smokr. In the former instance, the presrnce of the PAHs is traceable ro the previous use of coaltar forsealingpavemenrs.

The most common sou rces of the PAHs are diesel-engine exha ust and the smoh generated during rhe burning of wood, tobacco, and coal. Typically, they are adsorbed ro the consri1uenr soot particulates generated during combustion. Because many hea l')• duty truck s, buses, and moving equipmen t are diesel-powered, the PAHs produced dur· ing their use become components of the environmenrs into which their exhaust 11 discha rged. This is a matter of significant concern wh en the exhaust is inadequate! )' venred from enclosures.

During incomplete combus tion processes, PAHs are produced simultaneously with soot by a multisrep mechanism similar to that depicted in Section 5. 11. \'(ihen simplr hydrocarbons are heated ro high temperatures, molecular fragments-such as fm r~dicals-are produced. These fragments undergo reactions that result in the produc- uo~ of new molecules. Th e_ original molecules a nd their fragments dehydrogenm •:~ile ~he new m_olecules s!m1!arly fragment, amalgamate, and conti nu e 10 dehyd~oge- n e. '1hen deh}drogenar10n ha s occurred ro irs maximum extent , all that remains 11 soot or carbon black.

12.12-C ILL EFFECTS CAUSED BY INHALING PAHs

is~ complex m'.xt~re of_p~rricubte ma Her and gaseous com(:°u~d; h g oxide, carbon dmx1de, mtnc oxide nitrogen dioxide sulfur dioxitk,

me, ane, nzene, phenol. 1,3-buradiene, acro!c.-in, and the 1

vapors of several i~dividual PAJ-1;. Chapter 12 Chemistry of Some Hazardous Organic Compounds: Part

1

n,e p;i rncubte mailer co~~iSts mainly of soot to which the PAHs and orher compounds have JJsort-ed, \'{lhr:n they arc inhaled, the soot aggr:iva1es chronic respiratory problems.

Jnh.11:won exposure ro soot and crrta in ind1v1dual PAHs has also been linked with the onset of lung, and catdmva~cular dysfunction. Morem·er, massi,·e numbers of mutated crl!s emerge in t_he bronchia l passageways and bladders of indi \·idua\s who regularly inha le d1esel•eng_1~e exhaust, thereby causing lung and bladder cancer. 10.11 For this rea- son, soot is class1f1ed as a known human carcinogen.

The U.S. Department of Health and Human Services has concluded that exposure to JI ]east 15 PAHs causes the emergence of malignant tumors at the s11e of contact. The 010Jecu1Jr structures of these compounds are provided in Figure 12.7. These 15 com• p0unds are among c_he substances th.It the scientific community now suspecrs of niggering he onstt of cancer tn humans. 1

As previously no~ed, the particulate matter of tobacco smoke is also a source of PAHs, especially the following: benz(a]anthracene, benzolb]fluoranthene, benzo[,lfluoramhene, benz[ k ]fluoranthene, benzo[a ]pyrene, dibenz[a,h Jamhracene, dibenzo[a, llpyrene, indenoP,2,3-c,d]pyrene, 5-methylchrysene, and 7H-d1benzo[c,g]carbazole_l 2 These com- Pounds arc not cons~ituents of native tobacco le,n·cs but form when the tobacco undergoes 1ncomplrte co_mbust1on. They are suspected of collectively contributing to the onset of the canctrs experienced by tobacco smokers and individuals expo~d to secondhand smoke.

12.12-D PAHs A ND FIREFIGHTING Among modern-da y occupational settings, career-oriented firefighters are a major group of individuals most vulnerable to routinely inhaling PAHs. Fircfighms arc unwtttingl )· exposed to PAHs in at least the following ways:

Firefighters are repeatedly exposed to airborne PAHs adsorbed to soot particulates ar1·inually every fire scene.

Firefighters are also exposed to PAHs adsorbed to soot p:miculates in enclosed areas where diesel engines operate. Such areas include firehouses, where diesel-power equipment is regularly serviced and maintained and fire trucks idle for immediate use.

These repeated exposures to soot and the cancer-causing PAHs could constitute the basis for long-term health concerns for firefighters. Scientists denote soot and diesel engine exhaust as human carcinogens.

To protect firefighters against inhaling diesel-engine exhaust, the enclosed areas of firehouses should be \'entilated using a local exhaust ventilation system. As a general polic)', the idling of vehicles inside the firehouse should be avoided.

SOLVED EXERCISE 12.7

Wh!n em,ned from the exhaust p,pe of an 1dl,ng fire engine, d°'s the el".haust tend to corxentrate in the IO'Ner i;r upperreg1onsof an endosed f1 rehouse?

Solution: Becausedese!--eng,needldust is honerthan the temperature oftl1esuriound,nga1, ttrisestothece, l.ng or ooders1aeof theroofmanendosedf,rehouse Becausetheexhaustconcentratesnearthece,lmg,exhaustfarn UIOuId be located In the upper regions of ari enclosed firehouse to vent the exhaust to the outside environment

Chapter 12 Chemistry of Some Hazardous Organic Compounds: Part I 501

I

I I I I

'1 I J/11 , Nn l

I

FIGURE 12.7 Based on 1nlorMa:ionfromtheUS D~rtmt'f'II0fHeal1hand HumanServ-ces. 15PAHs are h~tlyto c.-iu}e CJncer rn ~hum<1ns Tht-y ar! p,oduc~ dunng the lll(Omple~combustionof ~ . petroieum,coal, andtobacco, andare c=utuentsofdiesel- ffll>SS1on&naustandcoal 1M The1rmo!ec1Jla1wuc- turesshowtna11heydre comp'vccom~unds CO!'ISIStlngofmutUdlly f\Mdbenztnenngs D1benzf.1,h)acnd1ne, d'benz{d,Jj.Kr,d,ne.and 7H-0:benzc[c.g/carbazole are~,cPAHs, meanmg mat tne,r mole'CUl.arnructureshave a n,ttogenat0minpldCe ofanngcart>ona:om ~tl'l~11!h tli!O\ U.S°'P,lrtrnffltof HNlll'ln:ll-!JJmM1SeM::1'S, f'utihcHNlttlSerw:t. N.JTIOl'lal lo«ciogyP,ogram. ~,o, to.n;:e Part.Nol'lliC.vohna, 1011 )

B<ru/apllthr.ict'ne Al!>Okno"nJ,BA

lkn.io(l]f!uor.1mhc:nc Al wJ.no,.nti B[A] F

O,bcn1[0,1larnd, nc Aho l no"·n as DB /a.J]AC

D,t:,,.-n,c,fll.r)p)rtne Al'Wlloo"n as D8/a.tlP

,,,,__ 11

'vV D1bcn10[0.flp)m11:

Aho l ll0\\na,D8[a,()P os dil>:n1ofd1J1,f,hl) }tr1C

&ruo(/J)f!~or.1n11't<!nc Ahol/lO"n.tiB[b/F

Bc:n.wja]P)l~OC AJ.-o)./1()\<n.isfl[a]P

D1 lx-n1/<l.h/an1hfactnc Al50 lnov,·n11DR l0.IIJA

D1bcnLO[i1Ji)p} ICIIC Also l no\\n as D8 [ll,11 /P

lmkll0/1.!J rd)p)rt-nr ,\l,o lnu .. n aslP

502 Chapter 12 Chemistry of Some Hazardous Organic Compounds: Part I

lknrnl;/fll>Ol'.11\lhc,-_, Al w l no11na~ R[J)f

""" C(XY N I N v- D,ticn,[11.lr/.w;nJ,~

Alw lno" n as DU[a.h)AC

SE # N I II

711 -D, bt-nw k.JIIC:irh.uok Aholno"O.l$71Hllt fr,,JC

D10Cn10[11,1Jp}rl'f'll.' Alsolno\\na, Dll [o.1JP

5-1'. lel h)lrhf)-Cll£' Abo l no"na,5-,\IC

12, 12·E WORKPLACE REGULATIONS INVOLVING THE PAHS ,\hhough a ?emussible t'~p?sure li_mit for diesel-engine exhaust has not bt-en publisht"d by OSHA ~r !\IOSH, the _li~11ts for tts gaSt>ous constituents are available. In this rexc, rhe ptrmiss1blt> expoSl'.re h~its for carbon monoxide, ni tric oxide, nirrogt"n dioxide, and sulfur.dioxide a.re ~is~ed m Table 10.2. OSHNNIOSH's publication of permissible expo· ,ure limits for individual PAHs as limited to naphthalene, amhracent", benzo[aJpyrt'nt', chrysene, pht'nanchre~e~ and pyrent- r apor. For naphthalene, the permissi ble exposurt' hrrur is 10 parts per millmn (50 mg/m ), averaged over an 8-hour workday- for the mher pi\Hs listed here, the \'alue is 0.2 mg/m3, a\'eraged O\'er an 8-hour workda;.

12,13 PETROLEUM AND PETROLEUM PRODUCTS Tht word petroleum is deri\'ed from the Greek pt tra, meaning "rock ., and Latin o/eum meaning "oil." The name "rock oil" is reminiscem of humans· earlie;t contacts with thi; rna teriJ l: a liquid that oozt"d from fissures in rocks,

12, 13-A THE NATURE AND NATURAL ORIGIN OF CRUDE OIL Perro!eum is a highly complex mixture consisting of many thousa nds of organic com- pounds, approximately 75% of which are h)·drocarbons, each of whose molecules ha s from 3 co 60 ca rbon atoms. The actual number of indi\'idual hydrocarbons in petroleum has been estimated to bt" be-tween 50,000 and 2,000,000. Petroleum occurs naturally det"p b(low Ear1h's surface in certain art'as around the world. Wells are drilled through rhe rock to 1he oil-bea ring stratum, through which the petroleum is then pumped co the su rface. In 1h1s fo rm, it is called crude oil, crude petroleum, or "crude." In the United Stam, major oil fields are located in Texas, California, Louisiana, Oklahoma, and Alaska, from which crude oil is transporied in tankers or transferred by pipeline, to plant sites known as petroleum refineries, where it is treated to produce petroleum products.

Although the mechani sm by which crude oil fo rmed in the earth is open to some dtbate, most scientists belie\'e that it originated from the partial decomposition of animals and plants (zooplankton and algae) chat li\•ed millions of yt"ars ago, Because geological forces caused the position of Earth's crust co change ovt'r the passing millennia, tht'se ancient organisms were buried at grt'at depths. Thei r decomposition resulted from the enhanced temperature and press ure at tht'se depths.

Both crude oil and natural gas formed when the remains of anciem organisms decom- posed , Crude oi l formed when the temperature was approximatdy 150°F (76°C), whereas natural gas fo rmed when the temperature rose to approximately 200°F (93°C). Scientists ~timate that approximately 13.0 pounds (5.9 kg) of crude oil resulted from the decompo- mion of 98 tons (89 t) of prehistoric matter.

A group of 14 Middle Eastt'rn and South American countries now controls a largt" portion of the world's supply of crude oil through a ca rtel callt"d the Organization of Petroleum Exporting Countries, or OPEC. This organization ext'rts comrol O\'er the sup- pl)' of crude oil b)' voluntarily restra ining production in order to stabili~e its price. Bttause the United Sta tt"S has an insatia ble tbirst for petroleum products, considerable efforts are now ongoing to shed U.S. dependence on foreign sources of crude oi l by replacing tbem wirhalternati\•es.

uude oil (crude petro- leum; The comple)(chemicalmi)(- turethatformsfrom naturally occurring bio- mauinsubsurface rock formations under high temperatureandpres- sureconditionsover geological time

fa cility engaged primar ily in producing on a commercial scale gasoline, kerosene, fuel oils, lubr!canu, and other products through fractionation, alkylation, cracking, blending, and other processes

petroleum product • My petroleum-based fuel such as gasol ine, jetfuel,kerosene,and heating oil, nonfuel like asphalt and lubri- cants, andpetrochemi- cals likeethane, propane, andbutane

Organization of Petroleum E)(porting Countries {OPEQ • The

12.13.9 FIGHTING FIRES INVOLVING CRUDE PETROLEUM Crude pmolt"um is a highly flammable liquid, because its fl ashp~in~ rang.es fro~ 20 to ~:~;;

0 w,~~s~~~~ec-

?O'F (- 7 10 32°C). Firt's in\'olving this material ha\'e oc~urre~ at oil f.ield~, 10 transit, ~ur- and unify common oil- ing pipeline transfer, and during storage. Ca pping burning oil wells ts a JOb fo r_s~i~lly marketing policies !rained t'X perts, but regular firefighters ha\'e also been ca ll~d on_to combat fi rt's mvo\\'mg among member crude oil at storage faci lities and during transfer and 1nns11 acc1dt"nls, countries

Chapter 12 Chemistry of Some Hazardous Organic Compounds: Part I 503

I'

l1

I

I

,non associated with theupulsionofcrude oil and the production of steam during a fire withinacrudeoil stor- ageunk.

fBctlonatlon (fractional

cm of separating mul- tiple components of a mixture based on the different boil ing points ofitsconstit\Jenu, dur- ing which thl! vapon arecollectedats~i- fied temperatures or withinspecifiPCltem- peraturerangMand subsequentlycon- densedto liquidsand collected

fractionofcrud epetro- leumobtainedbythe vaporizatlonofitscom- ponentswithina spe. cifictempera turerange followed by its condensation

eous fraction of crude petroleum that does not condense at room temperature,consist ing ofmethane,ethane, propane.and butane

lightnaphtha (llgrolnJ •The most volatile fract ion of crude petroleum

petroleum fraction of crude petroleum often used as the feedstock fortheproductionof gasoline

Alt hough small crude oil fires can be extinguished ~sing a del ugi ng volu most e:..-pem rrcommend the use ?f a~u~us film-for~1111g foam (AFFF) (Sec~~no~ ~·~ltt, as the most practical means of ex~111gu1shmg a crude oil fi re ms1d.e a bulk storage ta.n tBI ihese incidents, the use of water ,s recommende~ soldy for coolmg purposes. Water • In peiroleum are immiscible hquid~, and petroleum 1s less dense than water. When di~ha all(! on a peirolewn fi re, the water smks w the bottom of the storage tank, where it sen]~ a separare la rer and serves no useful purpose. iS

Furthennore, the presence of a water layer at. 1he bottom of a bulk storage tank a sp~ial concern fo r firefighters when combating a petroleum fi re. Although hpo5cs occurs at the t3nk's surface, wher~ flammable vap~r is emme~, t~e accompanyingth~~re combustion can be slowly transmmed b~ convect1~n and rad1at1on through the Under: ing petroleum to the water lay~r- Absorp110~ of th~ mte.nse heat causes the temperature ~ the petrolcwn and the underlymg water ~o nse until ~l11matel y, the water boils. Thewatti vapor then forces its w~y upward, pus~mg the b~rnmg petroleum_ up and over ihe walls of the storage rank. This phenomenon 1s appropm1ely called a bo1lover.

When a crude petroleum fire occurs !nside a storage rank, e:ery attempt should bt made to extinguish the fi re before the boilover occurs. The bummg, froth ing petrolt rhac spills outside 1hc storage tank has. been kno~•n ~o flow substantial distances from: tank, triggering numerous secondary fires. The firefighte rs who combat these fi res should be particularly wary, as the flowing, burning petroleum cou ld overtake unsuspecting fi fighters in its pathway. They must also anempt to confine water runoff to pm·tnt ad\·ersc impact on 1he environment and limit the department's liabi lity. n

12.13-C FRACTIONATION OF CRUDE PETROLEUM One of the major operations occurring at petroleum refineries is 1he fractional isolation of the substances in crude petroleum. The process is ca lled fractionation, or fractlonal disti~ lation, and is accomplished by heating the crude wi1hin precstablishcd temperature rangtS until its components vaporize. The vapors of these compounds then arc condensed mto liquids and collected in separate receivers. They arc referred to as petroleum distillatu .

. A single petroleum fraction may be used directly as a commercia l petroleum product, or 1t may be stored until it can be further processed. Bulk volumes of pe1roleum prodllCIS are tra nsported to major distribution centers, whe re th ey often are s1ored in rnulriplr tanks in a tank farm.

The fractions most commonly isola ted during the fractionation of crude pcrroleum arc represented in Figure 12.8. They consist of the fo llowing:

A gaseous mixture of methane (65% to 90%), ethane, propane, and butane. Tlus fraet1on, called petroleum gas, separates from crude petroleum at a 1emperarure bdow i0°F (21 °CJ. It is recovered and used directly as a feedstock for 1he production of othrr substances, or its components can be isolated to produce petroleum products such ll bottled gas.

A liquid mixture consisting mainly of alkanes a,id cycloalkanes IJaving from j 10 _11. carbon a~o~s per molecule. This fraction, ca lled light naphtha or ligroin, genera l!)' is isob red w11hm the boiling point range 158 to 284oF (70 tO I 40oC). At one rime, light ~::~:~a

0 7~; ~:e~ directly. as th~ fuel ~ormerly k~own as straight-nm gasoline. ~owew~

because it co~tai aphtha is no\~ considered env1ronmcmall y undesirable fo r di.reel ust, ihe Clean Ai r A;t a~ mu~h ~s 3 ¾, benzene by volume. (In 1995, using its authori ty under I%.) Toda Ii ht 'n PA h~lled the benzene content in petroleum produc1s to bs thJn toluene, an~ le x ,]:~~t?a IS used :is the f~dstock either for the production of benzen_~:

d I } isomers by ca talytic refo rmation, or fo r the production of elh) ene ~\ :i:~::::~::tc. cracki.ng. Jl

rb Sfing mamly of alka11es and cycloalkanes having from 7 to

504 ca o11 atoms per molecule. This fraction, called heavy naphtha, is generally isolated w11hrn

Chapter 12 Chemistry of Some Hazardous Organic Compounds: Part I

Gaseous <70"Ft <:21~) hvdroca1bon1

Kerosene

Diesel oil

>&98"ft>J70"C) Lubricating oil

Residue

Methane Uquefiedpetroleum gas(LPGI Llghterfuel

Stralght•rungasolln•

Motor gasoline Jet fuel

Tractor fuel Jetfuel Heating fuels

Diesel fuel Heat1ngfue\1

Crankcaseolls Hydraulic fluids Transmission fluids

Asphalt Pe11oleumcoke

FIGURE 12.8 Some prodvctsden~~bythe lract1onat,onofcrude petro!eum LJ quefed pet1oleum ga~(LPG)1s marketed 1ntheformthat come-sd,rectlyiromlr'e ds11llat,on 1ower. butthe otherlract,onsrequ1re furthe1relmemtntto remove undesirable com ponenis,m~tnotably, benzenearidwlfurous andnitrogenoo\com- pounds Theiehnement proctsses1ncludevacuum d1st1lla1Jon. ca1alyt1c reform mg,hydrocrad.lflg, andcatalyticcrack,ng

1hc boiling point range 284 to 392°F (140 to 200°(). It typicall)· is used as the feedstock for 1he production of motor gasoline. The production of gasoline involves catalytic cracking, during which hydrocarbons having from 7 to 11 carbon atoms per molecule arc produced. Thi~ fmtion is also the feedstock for the production of toluene. ;i:i~~nc~~d~np:~%'.rac-

1 A liquid petrole,mt product consisting of a/kanes and cycloalkanes having from leum often usl?d as a 9 lo 16 carbon atoms per molecule. This fraction, called kerosene, is often isolated tractor futl. jet fuel, within the boili ng poim range 302 to 527°F ( 150 to 275°(). Kerosene has been used as and heating fuel in the fuel in space heaters, portable cooking stoves, and water heaters and is suitable as a space heaters hght sou rce when burned in wick-fed lamps. Todar, kerosene is used primaril)' fo r the dlMel oil {diesel fuel , production of jet fuels. gas A fraction of

Ptr :,:ie~~;~d ;~::7r::,~~::::;'1:~ a;i!s?ic~~t:~;;:, l~~:t:go~:s 1~tu!~a~~ :~s:r::~ ~~~f~~Z:i~!;!ing within the boiling point range 392 10 698°F (200 to 370°(). In addirion to carbon and diesel engines h1·drogen atoms, the molecules of the component hydrocarbons may co~rai_n sulfur or lubricating oil (lubricant) rritrogen atoms. Diesel oil is blended with additives and used to heat buildi~gs and 10 1 Any fraction of power passenger cars pickup and heavy-duty 1rucks, buses, ships, and certa in types of peooleum oil 1hat is hcal'y equipment. Mo;e than 50% of the passenger cars now used ~y Europeans, and more capable of producing a than 90% of rhe ca rs in Italy alone are diesel•powered. In the United States over the past !~~a'::\ :,a~~~i~~e drcades, the use of diesel-powered passenger vehicles has fluctuated. . metal parn. so that

1 A liquid to semisolid fraction composed 0( polynuclear aromatic hydroror!'ons when used. It redum havi11g from 30 to 45 carbo11 atoms per molecule. This mixture of compounds ry_p1cally the fr iction generated 1, isolated at temperatures above 698°f (370°(). The products p~oduced fron., 1h1s f~c- between bearing hon arc broadly called lubricating oils, or lubrlcants. h typically 1s blended wtth various surfam

Chapter 12 Chemistry of Some Hazardous Organic Compounds: Part I SOS

f I/

I I I I I ii

I II/ 506

performance." addmvcs, corrosion inh1birors, and dcterg~ncs and ihen US('d as crank otl or hydraulic flrnd. Ir 1s also 1he feedstock from wh1Ch other motor and t;isi:

asp/ult • The dark brown-to·b!ackcement- hke residue that remains when crude petroleum is refin ed, usu•Jly combined with m1ner•!maner

Jubricanng oils are produced. Typically, this fraction JS hydrotreated and other cherrucal prOCC'SS('S ro remo\'e its undesirable coi:nponenrs-metals, to sulfur-and then blended tO achieve a Sj>fi:ified viscostf}', srabilif}•, and lubricit they are used, Jubncating oils produce an oily film that coats the surfaces of movi~~ :'11 paru, thereby reducing friction and wear. iii

The solid residue of the di~tillation process,, The fractionation residue is cal) asphalt, a mixture of compounds with molecules hav111g 40 or more carbon atoms As td igni tes at approximately 400°F (204°C). fr is used commcrciall~ as a componen~ llult rective coating, waterpro_ofing, and a~hesive products. Befo_re ns u_se for paving~ r:0- airfield runwa y, and roof mg construction, hot asphal~ often 1s held tn crucibles, asph•! kettles, and porra_ble tank trucks. DOT regulates Its transporcarion as an clevatt'd. temperature material.

uphaftkettle • Any vessel or container used to process,. treat. hold for heating. or dispense flammable or combus- tible roofing materials intheformof viscous liquids

alkyJation • Any peuo- leum rdining operation !nvofvingthecombina- tionofanalkane (u1ual/y isobutane)and ana!kMe,throughthe control of temperature andpreswre inthe pre:sMceofanaa d catafynandresutting lntheproductionofa branched<haina/kane

The hydrocarbons that are ~omponents of pttroleum fractions arc primarily com. pounds having carbon-carbon smgle bonds, but not carbon-carbon double bonds carbon-carbon triple bonds. Prior to their treatment, diesel oil, lubricating oils, and o, phalt usually contain sulfurous or nitrogenous compounds in addition to the polynuc]: aromatic h)·drocarbons.

12.13-D CHEMICAL TREATMENT OF PETROLEUM FRACTIONS The nature of the processing and chemical treatment operations cond ucted al mosi petro- leum refineries is noied in Table 12.14. One process is alkylation . This chemical reacnon produces a branched-chain hydrocarbon by the chemical union of an alkanc and an alkrnc. AJkylation generally is conducted in the presence of either sulfuric acid or hydrofluonc acid, borh of which act catalytically. The product of 1hc alkylation reaction is called an

ifriiiiiii Ma1or Treatment Processes Conducted at Petroleum Refmenes Thermal cracking and cata• 1 The breaking down of large hydrocarbon molecules into i:malltr lytic cracking of the con- hydrocarbon molecules by the application of heal or the Ult of Cili· stituentsofpe1ro!eum lysls fract ions Alkylation

lsomerization

Catalytic reformation

Steam cracking

Catalytichydrotreatment

Hydrocracking

The application of heat or pressure to produce a branched-<hain hydrocarbon fromanalkaneandalkene inthepresenceofsulfum acid or hydrofluoric acid

The rearrangement of a hydrocarbon molecule ha11ing a given num· her of carbon atoms to produce another molecule having the same number of carbon atoms

The reforming of alkyl cycloalkanes into aromatic hydrocarbons (e g. methylcydohexane - toluene) by passing the 11apor of a petro- /eum fract /on over certain catalysts at h1gh tempera1ure and pressurt

The production of ethylene, propylene, and the butane isomers. from :he ethane, propane,andbutane, respectively, in natural gas by react·

, mgthelatterwithstearn

The P_rocessing of a petroleum fraction with hydrogen .10 remoi·e su~ fur, nitrogen, heavy metals, and other impurities from its compontfl

The processing of a petroleum fract ion with hydrogen at high pres· sure and temperature to con11ert complex hydrocarbons into smaller ones for use as componenu in gasoline and other fuels

Chapter 12 Chemistry of Some Hazardous Organic Compounds; Part 1

alkyi'::~ B;~:,:~;;~:~~sl)~~:~~:~l: oft~n are prcseni at petroleum refineries in bulk stor• J!t The ~10s1 ~ommon alkylate prod:i~e~t~n~;:nd pose a fi re and explosion hazard. JS()O(l:Jl/e, but t_his nan~e is ~crua\ly a misnom: r. Th;';;r~leu~ mdustr)~ 1s commo~!y called It 15 producc-d mdustrially m massive amounts from rh~/'1:1e 15 2'7,4-mnmh)lpcmane. isobu1ene in the presence of a strong acid catalyst. mica] union of 1sobutane and

CH, CHi- r H- CHj(g ) + Clh ::c t - CH,f/.')

Cl l3

CH 1 1-l I I

Cl-l 1- C- CH1- ~ - C!i1(II

1-.ob,.i cnc CH1 CH3

, __ fr 15 also produced by the catalytic co~version of 1sobmene to diisoburylene (foomoie "c Table 12.5), followed by hyd rogenation. '

CH1 I -

K H1::cC- Cl-1 1(!1)

hobll1rnc

r H1 'f!h CH 1 CH 1 CH3-r - CH~- C= CH~(£l + CH 1 - 'f-CH : C- CH,(gl

CH 1 Cl\3 !.J .-1 Tn11"' lh) I 1 JX" ntcnc 1.J ,J Tnmc,h) l- ~•P,:nlclll:

/ CH1 H I I

2CHi - r - c H~- 'f-CH'1,gJ CH1 Oh

L !.~ fo mc1h)lr,,..ntlnc · 1-.00..tJni:"

Aside from producing 1rimethr lpen1anes, alkylation reactions also produce d1methylhexanes and other branched-chain alka nes. These compounds are desirable additives in gaso line, because the)' improve the completeness of its combustion. In rheir absence, the phenomenon called knocking occurs. This term refers to the "putt•putt" noises, i.e., audible pings, sputtering, and rattling, that are generated as the fuel burns wuhm the engine. Fuel additives that reduce the intensity of this knocking are called antiknock agents.

;i, lkyfo te • Any branched<h;,ln;, lkane resu\tmgfromthecom• binat,onofanalkane andan;,lkene

knocking • Thenoises associat,dwithth, incomplete combustion of a petroleum fuel, ,sptcia\lylnintemal combustion engines

pflroteumtu,l additi11e thatreducesorelimi• natesthenolsesgentr- atedwithin a combustion chamber when the fu el burns

SOLVED EXERCISE 12.8

n-Tnde<ane 1s an al1pha1rc al~ane havtng 13 carbon atoms per molecvle It 1s a constituent of a petrrneum d,st,llate co.~ected between 392 nd 698"F (200 to 37o•c) When n•tndecane 1s isolated from tht d,st l1ate and heattd or ti::io1e<1 to an appropn;te catalyst, 1t can decompose into n-octdne, propene, and ethene as shown be'ow

CH1CH2CH1C H1CH1C H2CHiCH1(Hp•-1iCH1CH2CH,(91 - n-lrC<'Cdoe

CH3CH1CH1C H1CH2CH1CH2CHi(g' • CH2 :(HzCH1·9. c..01~ H t>-Octi!Oi' P,OO<'f'

I/Jha tpe11oleum1reatmentprocess lsrepresentedby th,schem1calconvers,on?

Sotutlon: The eQuation represents an exam.pie of "crac~ing, ·ba ~""t~~u 9 ~~: :•~;~ ~'.:t;::: w:::;~

large hydrocarbon molecule 1s decompmed into ~mailer ones Y ,, . in911toacatalyst

Chapter 12 Chemistry of Some Hazardous Organic Compounds: Part I 507

I I

I

ii I

)II/

II I

i/11 I I 1/. 111

1111/

111/.11

/H

t II I 11

Motor guoline

motor guoline •The comptexm1xtureof hydroc.arbonscom- monlyusedasafuel for small veh icles

aviation gasolint • The complex mixture of hydro~rbonsthathas been blended with additwesforuseasa fuel inaviationrecipro- catingengines

octane number{octane

thatmeasurestheresis• tanceofagasol ine blend to knocking when burned in an engine, based on its comparison with the burningofamixtureof n-heptaneand 2,2,4-trimethylpentane

12.13-E GASOLINE . The following general cypes of g.,so/mc are produced at petroleum refrncries;

• Motor gasoline, the fuel primJnly produced by treating the hravy naphtha fracti ,ind b/C'nding ic wit.h oxygrnm·s (Sl-ct1on 13.2-F) and orhcr pcrformancr additii·et It~ us('d mainly IO (ud passtng('r cars Jn.d small 1rucks. .

Aviation gasoline. [he fud primarrl~ produced b} tn:a.r111g t~e kerosrn(' fraction db! d ng ir with d('icmg mhibitors (to ehmmaft the form:mon of 1cc) and man)· o•h

;;rfor:a~ce addim·es. It 15 ustd ma_mly to fuel a.~rcraft. Thr, terms .. aviat_ion ga>0Ji~~ and .. Jet fuel~ normally art differentt:ll_td 111 wda) s Jarg?n h) the r_n,mne_r m which th~• art inrtnded for ust. Aviation gasol~n(' ts us_rd to power aircraft ('ngm.es w1_1h spark plugs, where.is JO:-t fuel 15 us('d 10 pow.:-r Jtt turbme engines. Je_t fuels :ire .1dennfled by na rnts like JP-4, JP-7. and JP-8, wh('re ~JP~ i_s rhe acronym for Jet propulsron :ind the terrru '1.i] number designates a sprdfic composJtton.

The chemical composition of petroleum fuels varies, _nor only in differt'nt parts of rbr world bur also at different times of rhe year. The ehem1cal co111pos1t1on of a given furl produced at a refinery can even change dai ly. There are numerous constituent compo- nems of both moror gasoline and aviation gasoline, but most are branched-chain alkants. Hrdrorrea ring and hydrocracking com'trl ihe unsaru~ared hydrocarbons in the p,:,rroleum fraction used for rheir production into branched-cham alkanes, thereby yielding alhnts having 7 to J I carbon atoms per molecuJe in motor gasoline and 9 to l 6 ca rbon atom; per mo/,:,cule in aviation gasoline :ind jer fuel. These furls arc flammable liquids that po.t the risk of fire and explosion.

The different commercial types of gasoline are distinguished by 1h c-i r inheum octane numbers. The octane number, or octane rating , is a represrntation of thi antiknock properties of a fuel under laboratory or rest conditions. Ocrane numbers of zero :ind 100 are arbitrarily assigned ro n- hepra ne (a hig h "k nockc-,~ ) and 2,2,4-rrimerhylprntane (a low "knocker"). respectively. Heptane is an undc-sirablt fuel, becausr it causes engine knocking as it burns in a combustion chamber, bur 2,2,4-rrimt rhylpenranr /"isoocta neM) is a desirab le fuel, bec,1use its combustion don nor cause engine knocking.

CH3CH2CH2CH2CH2CH~CH,i n lkpll,ie

Ocla.itnumb,:r : 0

CH1 Cl-11 I

CH1-f- nl2 - CH - Cf-lJ

Cl-I; 2.2.4-Tnnwth) lp,;01:mc Oc1,mc nu111bcr " 100

T~e octane _numb~r of a gi\·en fuel is determined by compa ring its knocking v.~rh the knock'.ng of va rious mix rum of 11-heptane and 2,2,4-trimech r lpentane. When a sample of a fuel 15 found by ttsting to knock like a mixture of 85 parts 2,2,4-rrimerhylpt'ntane and 15 parts 11-hep1ane, rho:- fuel is assigned an octane number of 85. meth~~::ocrane rating of gasoline is commercia ll y measu red by 1he fo llowing tll'O

h Th_e Research_Octane Number, or R or RON, is dererrn ined by using a sampkof r e g_a~ohne as fuel 10 a trn engine wirh a variable compression ratio under conrrolltd :~;i;:::\:nf~e~;mparing rhe results using mixtu res of 2,2,4- rrimcrhylpenrane and

508

ing ,~el~~~~to; ~c::ne Nt~mber, or~ or MON, is determined in a similar ~~nnet u;· and variable i:~rion ti:i~;~me, bur wuh a prehe.:ned fuel mixtu re, higher engmesp« ·

The expression R + Mil is called rhe antiknock index. Chapter 12 Chemistry of Some Hazardous Organic Compounds: Part I

f here are three common gradfs of motor gasoline:

1 ,tegularf•g 8 • 2 ade gasoline. also call.:-d regular unleaded, \\ h1ch has a minimum ocrane

rJringo 1 Mid-grade gasoline, which hJs an octan.:- raung gre.1.ter rh.1n or equJI tO 88 and lrss

thMiorequal to 90 1 Premium-grade gasoline, also call('d supreme and super unleaded which ha s :m

antiknock mdex (R + .\1/2) grr.1.ter th.1.n 90 ' Byconrrast. rhe mdi\·idual iypes of a\•1a11ongasol1nr ha1·.:- 1:1r}'mg octane numbtrs, but all Jceorer 100.

At srrvic~ sra~JOns, cusro~ers ma y d1spensr 1he1rehoict' of grad.:- from fuel pumps like rhos.:- ~ho1~·n 111_ Figure 12.9 directly i_nro motor vehicle. A ytllow label r.:-scmbling rhe followmg is affixed to c:-ach pump ro tdrnt1fy the minimum octane rnting and rhe expres- sion /R + M)/2 MET! 10D:

MINIMUM OCTANE RATING (R + M)/2 METHOD

re9ular•9ro1de g~so1ine (itgul.trun! t aded) • Thegr.tdeofgaso!ine h.tvingamlnimum octane rating of 81

mid-gr.tde gasoline

having an octane rat ing greater than or equal to88and less than or equal to90

premium•grade gaso- line (supreme. super unlu ded) • Thegrade of gasoline having an .tnt1knock index greater than90 JP-4 JP-5 93

Thelart" ,s rhe mrngc of rhe ,cse,,ch ocrm ,umbe,'"d rhc mo10,ocra1,enumbe,.

fl(iURE 11 .9 The d,fferent grades ol gasol,ne fuels a·e d,ffe·enuted by the:'. ooane num~rs. wh•ch are estab- llhed by subJectmg a gaso line samo'e to test CO'ld1t1ons that ascerta n how we,1,t ~nocb when 1gnrted 1n a com-

1 IJl.st~ chamber At these fuel mos, regular, mid-grade, and prem,um gasoline fuels Mv,ng octane numbers o 87, 89, and 91 respectively ar~rowied forsa'e As reou, red t:y u S federal Trade Comm,~•on regulations at 16 C FR §30612: the octilne ~umbers are pnnted on labels in tilac~ on a ye'1ow background (CQl.l'1eSyoif!¥')e~)

Chapter 12 Chemistry of Some Hazardous Organ ic Compounds: Part I 509 I

r unlud~g•so!lne notconta,n • h.•ad compoynd svch as tetr•~yllead, formerly an addtt,ve tha t functioned iitS an an1ilo:.nock.tg~t

Diewloil

All ty~ of gJ.solmt sold in the Umred States smcc 1975 are referred to as lln le gasoline. meamng ihar they do ~ot coma m rccrnn,iechyllead, wraechyllcad, or oihe, idtt1 b.iSN addmres. Using the aurhomy of thf' Clran Air_Act, EPA ban nrd /Cid USt' of 1~.id compounds 111 gasolmt> to protoct a_utom?t1 ve Ca13 lyt rivail!"d by !rad and to a\·oid the unnecess.1ry dispersion of le:id throughout the c

As previously notrd 111 St'CtlOII 5.8-A, ro reduce the vol ume of carbon operating mocor i•t-hlcles emit to the atmosph: re, the federal governm('nt is rrquir in bJ· 2016 and 2025, the flem of auto co~1pa111('S must a1•erage 3!.5 mi/gal (15 krnf1.g1h.i1 54.5 mi/gal (23 km/L), rrspecti1·dy. This almost doub/('s roday s average of 27 5

~nd ( 11. 7 km/L). . 11'~1

12.13-F DIESEL OIL Diesd oil is the furl used ro powrr diesel engines in cenain vehicles and mach ' . flashpoinr ranges from I JO to 190"~ (43 to 8.S"C). In the United States, dicsrl 0:~;;~r: duced from the fraction .of crude 011 that rrfine~s call sour crude. Because this fractiori conrains sulfurous and mtrogenous compoun_ds, II mu~t be trea1~d to reduce or elimi~ie the sulfur :md nitrogen content to comply with todays Clean Arr Act standards. Tha

11 accomplishrd by hydrogenation. The process, cal!e_d hydrotreatment, produce'! 3

dits(I oil consisting of alkanes, cycloalkanes, and ~romanc compoun~ s. During hydrotr~ting, 0e sulfur and nirrogrn atoms are com•erted mto hyd rogen sulfide and ammonia, resptt. CJvely, and removrd from the fuel.

U1Jdeo,l orthefraction thereof that contains sulfurous and nitroge- nous compounds

petroleum refin ingpro- cessthatupgradesthe quality of petroleum fractlonsbyusing hydrogen to reduce or elimlnatetheirnitrog- enousandsu/furous content and to convert alkenestoalkanes

Umreatrd and hydrorreated diesel oi l are sometimes referred to as heavy diesel oJ and light diesel oil, mprcrively. The combustion of untreated dirscl oil yields a SOOI}· smoke consisting of particuk11es to which polynuclea r aromatic hydrocarbons adsorb. As notrd in Section 12.12-C, the production of this plume poses a risk 10 public health and the environment, brcause inhalation rxposu re to PAHs is linked with the dndop- ment of malignant tumors in the lungs. The combustion of ligh t diesel oil yieldi an emission that contains fewer pollutants. To comply with the Clean Ai r Act standard established fo r finr particulate matter (Section 10.9-D), the American diesel indusm· brgan changing from heavy 10 light diesel oil in the mid-2000s. Today, light diesd o~ is thr ma in fuel used in diesel-powered vehicles that arc dri ven on U.S. roadways.

The different commercial types of light diesel oil are ra red by a system similar to th{ octane-numbrr syste m used for raring different t)'pes of gasoline. For diesel oils, n 11 cal/rd the cetane number. Whereas the octane number meas ures the abi lity of a gaso- line fuel to reduce engine knocking, the cetane number gauges 1he case with which l diesel fuel auroignites when it is compressed in a cylinder of a diesel engi ne without a spark plug.

cetane parameterthatmea- suresthecombus-tlon qualityofdieseloildur- ing iu compression ignition

Cetanr is the common name for n-hexadcca ne, an alkane having the formula C10H;.i. For tesr purposes, the cerane number of 2,2,4,4,6,8,8-hepramcthylnonane and crtane arr arbitrarily set ar 15 and I 00, respectively.

fH1 y'·l3 THJ y 1·! 1 CM1-y-CH2-r - CH1- CH - CH2 - y - CH 1

CH3 Cl·h CH3 2.2.~A,6.8.S. /kpu 1nc1 ll}lnon~ 11e

C,·1.incnumOCr "" 15

CH3CH2CH2CH2CH2CH~CH2CH2CH2CH2CH2c 1-12c H2CH2CH:CH3 11 1ln.ide(J.Oc(C,·1anl'f C, 1:vic nu111bcr 100

510 Chapter 12 Chemistry of Some Hazardous Organic Compounds: Part 1

['he crtJnl' numhcr of a diesel fuel is deiermmrd in irs! ,ngines. . specia l \·anablc-comprcss1on-ratio

Generally, d1esc- l engines operate well h h 1,crween 40 :md 55. The 1wo diesel fud t . w en f e diesel ful'I has a Cl'tanc number egular-grade diesel oil and premlum-gra~~l'~I ava;la_blr c~mm~rcially arc rcfe rrcd to as

:ng from 40 to 60 and 45 ro 50, respectively. ese oil, whrch hne cctane numbers ra ng·

12.1 3-G HEATING OILS 5ome petroleum produces are useful as heating ·1 Th ~tion, followc-d by blrnding with specified additii•: 1 ~ore? ;re produced by framon- naphtha often are proccssed to produce hcatin, ~i ls eit~c/!'• diesel f~el and h~avy 11•11h'.n a narr?wcr d1s1illarion range or by adding! spe~ified amo~m~e;::~~1;rs fracuons until thc frna! blcnd possesses de'i irable ignirion temperatures and ~eat (Btu) values. These pro?ucts used as fuels in home furnaces and boilrrs for focroril's , apartm~n t anfd offi~e buildings, schools, and Stram-powered vessels, as well as for thl' grner:1 non o clrctr1c 1ty.

Six grades of heating oils are commercially recognized in the United States, each des- ignated by the words Fuel Od followed b)' a number from I to 6. The grades are com- postd o~ hrdrocarbo.ns _ha~i_ng 14 to 20 carbon atoms per molecule and arc commercially d1snngu1shed by their 1gnmon temperatures, rach progrcssh·ely increasing in the range from 444 °F (229°C). CO 7~5°F (407•q, In the United States, Fuel Oil No. 2 is the most commonly used hea tmg 01I.

12.13-H TRANSMISSION OF CRUDE PETROLEUM ANO PETROLEUM PRODUCTS BY PIPELINE

Crude oi l is f~eq uenrly transfer~ed by a nerwo~k of pipelines from.oil fields imo stor:1gr tJnks where 1t awau s processmg. In the Umted Siate'i , approximately 55,000 mi les (88,500 km ) of transmission pipelines transfcr crude oil from spot to spot. Similarly, all t)'pes of pe1roleum products arc regularly transferred by pipelinr from refinrries into stor- ase tanks awaiting an end-use.

A single pipeline used co transfer crude oil or a pet roleum product may be either aboregrou nd, underground, or both. Portions of the 799-milc ( 1242-km) Trans-A laska Pipeline System pm·iously notrd in Section 10. 15 are both located underground and ele- 1ated alxll'eground. The pipeline is used to transfer hot crude ml from the oil fields in Prudhoc BJ)' to Valdez, the northernmost ice-free American port. The crude oil then is transported m bulk by ca rgo ships 10 the west coast of the United States, from wherr it is again trans- ferred by pipeline to refineries.

At 49 C.E R. S 195.410, DOT requires the posting of line markers like thosr shown in Figure 12.4 co indicate the approximate location of petroleum-transmission pipelines. Like the line markers used for locating natural-gas-transmission pipelines, the line mark- ers for abol'eground petroleum-transmission pipelines must be placed along each section 1ocared in an area accessible to the publ ic and post('d along right-of-ways and at road, railroa d, and wa1crway crossings. .

A major lea k of crude petroleum or a petroleum product from a petrolrum-transn~1s• 1ion pipeline constitutes a major fi re and explosion hazard , and may also ca_use a ma1or tnvironmcnra l disa ster. Jn 2010, a failed valve was the cause of a ca tastrophic leak fjom the trans-Alaska pipeline that resulted in the release of over !00,000 gallons (378 m_ ) ~f cnrde oil to the environment. The oil was collected in a containment system from which LI was thereafte r retrieved. A ma jo r disaster associated with the lea k wa_s a.\'Crted onl y btcausr the prevailing temperatu re was 50 cold that the oil w:1s unable IO 1g111te.

Htatlngoi15

regular-grade ditsel oil • Oitsel oil ha~1ng a cetanenumberranging from40to60

premlum-grade dlesrl having a

cetanenumbrrranging from4Sto50

heating oil • Anyprtro- leumd,stillateused direalyorasa blend to fuelfurnacesandboll- ersmresidences,large building1, andf11ctories

Chapter 12 Chemistry of Some Hazardous Organic Compounds: Part I 511

Comider chi: following Lewis srructures of rhe chlonnated dem·.Jtn•es of mrthJnr;

H - C-Cl

\fi:1 h)IChlomk (Chloro,.....1h~ll<C I

H H T' CI - C - CI CI - C - CI Cl - C - c1

I I I H Cl CJ

\k!h)knc d1Jondc (O,,hlorortl<'lhancJ

Chlmofonn (Tnchlonimc,th;,ncJ

C.lroOnt~lr;ichl<mJc- !T .. 1r.,cltl"rot1ic1JwicJ

From lefr to right, each structure iden~ifies an organic compound in which one, f'.l·c three, and four hydrogen atoms, resprcuve(r, have been substituted with c~!orine Jfoni~ These compounds are known mamly by thc1.r common ~a mes: methyl chloride, methylcr~ ch loride, chloroform, and carbon tetrachloride, rcspcct1velr, ,

ln the IUPAC system, the halogen atoms arc named as substJt~cnts ~f the compound h.ii. ing the longest continuous chain of carbo~ atoms. _As first noted m Section 5.14, thr haKlgr:l atoms are named as substitucnrs by rcp!acmg the -me suffix on the name of the halogen llit& -o. The number of halogen atoms is indica ted by the use of mo110-, d,- , tn-, tetra -, and !O forth, for one, rwo, three, four, or more atoms of rhc same halogen, respectively. Henct, tit IUPAC names of rhc chlorinated derivatives of methane are chloromethane (rhe mono-~ is droppro), dichloromethanc, trich/oromethanc, and retrachloromethane.

•M'frliliHifiifll

5 14

1hr ma1or compooent 1n the fore suppressant k/'IOWTl as Pyro•Chem FM-200 1s 1. 1, 1,2,3,3,3-heptafluorOl)l"Ofl""f - Show how th,s name 15 used to determine the mo!Ku1ar formula for tli1s substance

Sollltion: The name of this fire suopressant md,cates that 1r 1s a fluonnated derrva t1ve of propane, whostcher-.- cat formuta 1s C3H1 The use of ~ta If\ 1he name of the lire suppressant means that seven of the e,ght Jtyc;~ atomsm propane have be-en replaced with f!uonneatoms The notation " 1, 1, 1,2,3.3,3" 1denul,,s prw~~wr.:- hydro;,n atoms a!Qrlg tne three-<arbon-atom chain have been replaced with fluorine atoms Thrtt ~VO'"~ atoms replace the three hydrogen atoms that ar, bonded to each of the first and tli ,rd carbon atoms. ~nd I)',! f!UOMe atom replaces one of the hydrogen atoms bonded to the Set'.ond carbon atom ConseQuently, the l"OIK· ufar forrr,u!a of Pyro-Chem FM-200 is the following

FF F I ' F- C-C - C- F

I I I F H f

Th,s formula may bt conde~ to CF3-<Hf:--(F;

The molecular s1rucrures and names of several chlorinated derivat ives of erhant arr noted below:

CHJ- CH1CI Chloroc-1h;ii-1,· l.f -D,chlonx1h.mc 1.2-Dichloroc th:rnc

C! - CI-I - CH1CI CJ

Cl - CH - 0 1- CI I I

Cl Cl

Cl

Cl I

c 1- C- CH3 I

Cl Ll,1 -TnchloroclhlM

I CJ - C - Gl2CI

I Cl

l , l .2•Tnchlora.-1hanc I. J.~ .l Tclr.l( ~/,,nicttun,•

Chapter 12 Chemistry of Some Hazardous Organic Compounds: Part I I. J, ),J TCIIJChl,)rOclh:lllC

The molecu lar structures and names of the ch lo ri nated derwaU\'es of ethenc- arc nottdnes t:

Cl II \ I C,: C I I

11 I!

Cl Cl I I C= C I I

fl H ' "I~ D,chl<1rocth,n,:

Cl Cl \ I C= C I \

Cl II Tn,hloror-thrn,:,

Cl H I I C= C I I

II Cl

Cl Cl \ I C= C I I

Cl Cl Tr1r:1..hlon:,e1hrnc

Cl II I I C C I \

Cl II

Each of these simplc chlorinated hydrocarbons is a colorless, wa1cr-insoluble, high! )' ,·obrile liquid/ most a_re nonfl~mmable. For decades, this combination of physica l propcnies vns the rechmcal basis fo r their popular use by many manufacmring :rnd process industries. for ex:t mplc, trichloroerhene, 1,1 , l -trichloroethane, and l ,1,2.2-tt1rachloroethane were once popular industrial degreasers. These liquids were used to cff«tively clean oil, grease, \\'as, and other undesirable material from metallic, textile, and glass surfaces. Ca rbon rmachloride once was m ed as a fire-extinguishing agent. Methylene chloride forme rly was widely used as an aerosol, and is still used as a solvent. Tetrachloroethenc, also ca lled pmhloroethylene and perc, is still used as a popular dry-cleaning agent in many stat es, although in southern Ca lifornia, its use is illegal in new and upgraded facilities.

Whtn inhaled, the vapors of rhese simplr chlorinated hydrocarbons can ca use cancer. Furthermore, when released to the environment, 1hcy deplete s1ra1ospheric ozone. One by ont, the simple chlorinatcd hrdrocarbons ha ve been replaced in the modern world with othtr substances that perform as well for a specific purpose but do not cause cancer or deplete stratospheric ozone. Chemical companies are still actively sea rching for substances 10 replace tetrachloroerhene as an economical dry-cleaning agent because 1hc days of its ust are probably numbered. One nonhazardous agent that has been chosc-n for this pur- post is a mixture of banana and orange ex1rae1s.

12.14-A ILL EFFECTS CAUSED BY INHALING THE VAPORS OF THE SIMPLE HALOGENATED HYDROCARBONS

When the vapors of the halogenated methanes and etha nes are inhaled at relativelr low conccmrations, the)' usually cause lighthcadcdness, dizziness, and fatigue. However, when they arr inhaled at concentrations above their permissible exposure limits, they ca use a lowering of consciousness that can be life-threatening.

Inha lation exposure co the v.ipors of the following halogenated hydrocarbons causes cancer in laboratory animals: bromodichloromethanc, carbon 1etrachloridc, chlo roform, 1,2-dichloroethane, hexachloroethane, mc-thylene chloride, tetrachloroethene, tet rafluo- roNhene, and trichloroethene. EPA classifies trichlorocthene as a human carcinogen, 13 bur the ocher halogenated hydrocarbons in this list generally are ack nowledged to be probable carcinogens,

12.14-B TRANSPORTING THE HALOGENATED HYDROCARBONS When shippers offer a halogen.ired hydrocarbon for 1r::mspor1?tion, _D~T requires them to enrer th e rel evant shipping description on a n accompanying s~1pp1~g paprr. Some CX3 mples for severa l representative ha logena1ed hydrocarbons arc listed m Table 12. 16.

IJ "Toiucologica l Review of Tr ichloroethykne~ (EPA/6J5/R•09/0IIF) IWash1ng1on, DC: U.S. Em·lronmrnul Prot«:t,onAgency, 1011),

deg re<1str•Any organic compound used as a solvent to remove grease and oil from surfaces

Chapter 12 Chemistry of Some Hazardous Organic Compounds: Part I 515

I I

Ml'thylene chloride

chlorofluorocarbon (CFq • Any compound whosemoteculesare composed solely of carbon, chlorine, and fluor ine atoms

8/Hiliiii Shipping Desmpbons of Some Representative Halogenated Hydrocarbons HALOGENATED HYDROCARBON OR GROUPS THEREOF

Al\ylchloride

Carbon tetrachlo ride

Chlorod 1fluoromethane

SHIPPING DESCRIPTION

UNllOO, Allylchlor1de, 3, (61), PG~ )------

UN1846, Carbon tetrachloride, 6.1, PG II (Marine Pollutant)(Po. UNI0l8, Chlorod1fluoromethane, 22 o, UN101 8, Refr igeratedgasR-22, 2.2

=Chcclo-,o-;-fo-,m-----r;;;UN:;-;1;;888;;-,;;Ch;;loroform, 6.1, PG 111 (Poison) ---- Chlorotnfluoromethane UN1022, Chlorotrifluoromethane, 2 2

o, UN1022,Refrigeratedgas R-13, 2.2 0,,-:-,_=-0,-:-,,,--,0,-0,-::lh-.,:-,---T, ~UN;;,;;,.,,_-;-,_;--;,_o;;:,,:;;hl;;:o,=o,:;;,,;:.,;:,,-;,-;_ ,;;c;;-,,----

~,,~,-,-,oo-, ccdi~lh,-lo,~,d~,.---,~U~N~ll"~~. ,~lh~,,=eo~,d;;ic:;;h,=o,~,d~,. ,3,o,pc~,~, ---- Methyl bromide

Methyl chloride

Methylene chloride

1,1,2,2-Tetrachloroethane

Tetrachloroethylene

1,1,1 -Trichloroethane

Trichloroethy!ene

UN1062, Methyl brom ide, 2 l (Poison • Inhalation Hazard, ZOlltQ I UN1063,Methylchloride,2.I --

o, UN1063, Refr igeratedgasR-40, 2.1

UN1593, Dichloromethane, 6.1, PG 111 (Poison)

i UN1702, 1, 1,2,2-Tetrachloroethane, 6 1, PG II (Poison) (Marint I Pollutant) UN1897, Tetrachloroethylene, 6.1, PG Ill (Poi1on) (Marine PolliJtanu

UN2831, 1, 1, 1-Trkhloroethane, 6 1, PG Ill (Poison)

i UN1710, Trichloroethylene,6.1, PG Ul(Poison) •E1hytenedl(hlo1ide.tnd\,2-d1(hloroeth•ne.t1esynonym1.

DOT also requires shippers and carr iers to comply wi th all applica ble labeling, marking, and placarding requirements.

12.15 CHLOROFLUOROCARBONS AND THEIR RELATED COMPOUNDS

A special grou p of halogenated hydroca rbons are the chlorofluorocarbons, or CFCs. Their molecules contain only carbon, chlorine and fluorine atoms. They fo rmerly were impor- tant commercial compounds, but for reasons soon to be discussed, their use has bttn sharply cunailed worldwide.

The commercially important chlorofluoroca rbons used in the past were primw!r members of the following classes of substances:

• Chloroflitoromethanes, These compounds have the gene ral chemical formulJ CF ,Cl,._., where x and 11 are whole numbers less than 4.

• Chlorofl,mroetha11es. These compounds have the general chemical formula C2F~Clr,• where x and II arc whole numbers less than 6.

As a class of organic compounds, the chlorofluoroca rbons are relatively inert su~· stances. They readily vaporize at room temperature. Although many are nonflammJb r gases, some are flammable.

516 Chapter 12 Chemistry of Some Hazardous Organic Compounds: Part I

Thr chlorofluorocarbons typically were pre db commercially available chlorinated hydroca.rbo~~r;or !' react ing h}drofluoric acid w11h a romethanes was prepared from carbon tetrachloride as fu

1 :~.:; a mixture of chlorof\uo-

KCllg) -i- JHI·(/) --. CCl~F2(g) .,. CChF(~) .._ JHCUg) c,rt,.:,nlctl'3<.hlon,k ll)<lroOuonc~,J 1)1ehle)!OO,nuorolllt't~ ln<hi-,m!l~unor,,rth.m,: lhdr(>fen<hlon,k

The two chlorofluoroca rbons were then separated by disullation. Some examples of the CFCs and '.heir related compounds, hydrofluorocarbons and

h)drochlorofluorocarbons, are n~ttd in Table 12.17. Aside from their chemical names they ar~ .also k~own by com.merc1a\. names as CFC-u,xy:, or R-wxy~, where w, x, )', and , are d1g1ts derived from their chemical formulas as follows:

w ,.. the number of carbon-carbon double bonds per moll!CU!c x ,.. the number of carbon atoms per molttule minus one y =- 1he number of hydrogen atoms per molecule plus one z - the number of fluorine atoms per molecule

When w, x, y, or l i.s zero, the digit is omitted. For example, 1u, :t, )', and z fo r the ch!o- rof\uoroc~ rbon having the formula CFC\3 are 0, 0, 1, and I, respec1ively. It is denoted commerctally by the product names CFC· 11 or R-11. Usmg the \UPAC sys1em, n is named trichlorofluoromethant'.

Sometimes, it is necessary to distinguish between two or more structural isomers of the chlorofluoroethanes in their commercial names. The compound within a group of these isomers having the smalles1 atomic mass difference on each of the two carbon atoms is denoted without a letter. A lowercase a, b, c, or dis appended to WX)'Z to differentiate 1he isomers as their masses diverge from this difference.

As individual compounds and blends thereof, the chlorofluoroca rbons once were widely used for the following purposes:

I Refrigerants and coolants in residential and commercial refrigemion and air-conditioning equipment, including refrigerators, frttZers, dehumidifiers, water coolers, ice machines, and air-conditioning units (including automotive air-conditioning units). The CFCs were first commercially introduced into the U.S. market in 1931 as safe ahernati\·es to the flammable and toxic substances then in common use fo r cooling: methyl chloride, sulfur dioxide, and ammonia, In commerce, they arc known ooUea:ively as Freons, or Freon agents. Cleaning fluids fo r electric, precision electronic, and photographic equipment and for maintaining aircrah . _ .

I Foam-blowing agents by extruded-polystyrene (Section 14.2-Al and n~1.d-poly'.1rethane• foam man11faciurers (Section 14.9). Because the CFCs ha\'e low ~oihng points, the}' readily vaporize when mixed with hot plastics. The bubbles of t.h~1r vapors caustd the plastics to expand until the)' resembled frothy mi>:tures that sohd_1fied as foams. These foams were 1hen marketed commercially as insulat10.n and packaging. ~erosols for dispensing cons~lfller products containenzed inr m:t:~::· :~F~ t~r~ is ~lieved ro have. releas~ m.to the. aun~_phere fal~~te te~s to ·de fixed amoums. refrigeration and alf-rondmomng uruts, v. hich use c .. rs b~ .

1 cu

When mixed with rthylene oxide, sterilizers of heat-sens'.t1vc reu·sa· e osp1t_a appara s. A general inhalation anesthetic in hospitals and ,·ctermary chmcs, espmally the com- pound known commercially as halothanc, or fluothane.

Cl F I I

Br-C-C- F I I H F

2-Hmmo-!-chloro-1. 1.1 tn!lu~tlunc i l\l llllhJl'lc)

T1trachl010• 1th1n1

t Carbon

t1tr.chlorid1

Fr, on(freon ag,nt,) • Thetrademarkofany chlo1ofluo1ocarbon, hydrochlorol luorocar- bon, and hydrofluo10- carbon used a1 a foam-blowing agent or refr igerant

Chapter 12 Chemistry of Some Hazardous Organic Compounds: Part I 517