321
2
Root or “last” name = pentane
3. Now we need to give the name and the address of any substituent attached to the
longest chain. For alkanes these substituents will be carbon chains also. They are often
called “side chains” because the come off the sides of the longest chain. They are also
called “alkyl groups” because their names are the same as alkanes, except the end is
changed to –yl:
Alk ane Alk yl
CH4 methane CH3- methyl
CH3CH3 ethaneCH3CH2- ethyl
CH3CH2CH3 propane CH3CH2CH2- propyl
…etc.
Memorization Chapter 6
Organic Chemistry Part I
I Alkanes
A. Naming
Memorize: ethane, propane, butane, pentane, hexane, heptane, octane, nonane, decane.
Know molecular, structural, condensed structural formulas.
methane ethanepropane
CH4 CH3CH3
CH3 CH2 CH3
butane pentane
CH3CH2CH2CH3 CH
3 CH2 CH2 CH2 CH3
hexane
….and etc.
CH3 CH2 CH2 CH2 CH2 CH3
Know the IUPAC Naming system:
1. Find the longest continuous carbon chain. (Be careful to choose the longest chain,
even if it is not written straight across.)
2. Give "last name" based on the number of carbons in that chain.
Example
5
CH3
CH
2
CH
5
CH3
CH2 CH3
44
31
2 3
2. Assign root name: pentane
3. Find subsitituents:
methyl 3
2 3
1. Find the longest continuous chain:
3
And, of course, since alkyls are attached to the main chain, they must be missing one H
atom compared to the alkane with the same name. In our example the substituent is a
methyl side chain:
5
2 3
ethyl
So this will be an ethyl methyl pentane, but we must number the main chain, in this case
from right to left,
methyl CH3
5 4 3 4
3
CH3 CH2 CH CH CH3
2 1 2 1
CH2CH 53
ethyl
It is 3-ethyl-2-methylpentane
321
2
So this is a methylpentane. Now we must give the address of the methyl group; that is we
number the main chain and note the number of the carbon to which the methyl group is
attached: 3-methylpentane. We number the main chain from the end closest to the
substituents, or if more than one substituent is on the chain, number from the end that
gives the lowest numbers for the addresses. Notice that we use commas between
numbers and a hyphen between a number and a word.
Another Example:
CH3
CH3
CH3
CH3
CH2
CH2
CH2
CH
2
CH
C
H
C
H
C
H
C
H
C
H
C
H
5
CH3
CH2
CH
3
CH
CH
C
H
C
H
C
H
C
H
C
H
C
H
CH3
CH3
CH3
CH3
44
31
3-bromo-2,2-dichlorobutane
B. Physical Properties
Halogenated alkanes are also nonpolar, so they do not dissolve in water,
but dissolve in other nonpolar compounds such as oils and greases. They
have the same physical properties as alkanes.
C. Physiological Properties
Chloroform (trichloromethane) was used as an anesthetic, but has been
replaced because it is carcinogenic. A commonly used anesthetic is
halothane: 2-bromo-2-chloro-1,1,1-trifluoroethane (draw it – it’s not too
hard!) Carbon tetrachloride (tetrachloromethane) is used as a solvent and
it is, like chloroform, toxic.
D. Chemical Reactions
These are similar to alkanes.
B. Physical Properties
Up to butane alkanes are gasses at room temperature (25o C) and pressure
(1 atm). Pentane to decane are liquids at room temperature.
All are very non-polar and hydrophobic; they will not dissolve in water.
Nearly odorless, tasteless, colorless.
C. Physiological Properties
Low molecular weight compounds such as pentane to decane dissolve oils
from skin. Higher molecular weight compounds are oils. Low molecular
weight compounds are either gasses or are volatile, in either case the
vapors tend to be anesthetics. Some people will sniff these compounds to
get a mild "high", although this term is misleading because they are
depressants rather than stimulants. Inhaling the vapors can also cause
nausea, vomiting, and eventually lung, liver and brain damage.
D. Chemical Reactions
The alkanes are considered unreactive. They can be mixed with a variety
of chemicals such as acids and bases without undergoing any reaction.
They are all however flammable.
II. Halogentated Alkanes
A. Naming
The naming is the same as alkanes, except name F, Cl, Br, and I
substituents as fluoro, chloro, bromo, and iodo respectively. Note that
ordering of substituents in the name is alphabetical.
Example:
134
CH3
Cl
C
2
Cl
C
H
Br
CH3
III. Cycloalkanes
A. Naming
The root or last name is formed from the number of carbons in the ring, by
adding the prefix cyclo. A three carbon ring is cyclopropane, four carbon
ring is cyclobutane, etc. For cycloalkanes with substituents, the carbons of
the ring are numbered such that the number one carbon is one that has a
substituent, and you number around the ring such that other substituents
have the smallest number for their address.
Example:
1,2-dimethylcyclohexane
3
2 2
B. – D. Properties of cycloalkanes are the same as alkanes in general.
IV. Alkenes (C=C functional group) and Alkynes (C
≡
C functional group)
A. Naming
They are named in the same way as alkanes, except: 1. Choose the root
name based on the longest continuous carbon chain that contains both
atoms of the double or triple bond. 2. Give the number of the carbon at
which the double or triple bond begins. 3. Change the ending of the root
name from -ane to -ene for alkenes, -yne for alkynes. For rings that have
double bonds, the carbons in the double bond are always #1 and #2.
B. – C. Physical and Physiological Properties
Same as Alkanes
D. Chemical Reactions
Addition reactions (see Chapter 10).
V. Benzene
A. Names
Name with benzene as the last name. Use ortho-, meta-, para-, for
disubstituted benzenes; use numbers for benzenes with more than two
substituents. An HO- attached to a benzene ring gives phenol, CH3-
attached to a benzene gives toluene, NH2- attached to benzene gives
aniline.
B. Physical and Physiological Properties
Benzene and toluene are nonpolar and unreactive, and are therefore
important industrial solvents. Benzene, however, is carcinogenic, and its
use is therefore limited. Phenol is an antiseptic, and its derivatives are still
widely used (in Listerine, for example). Aniline derivatives are important
pharmaceuticals such as acetaminophen (Tylenol).
C. Reactions
CH
H2C CH
H2C CH CH3
HCCH
Benzene is unreactive. Its double bonds do not undergo addition of H2,
Cl2, or water as easily as alkenes.
