ORGANIC 2 DISCUSSION RESPONSE

Catarina Smith

-o +

* - a

1 ,3 product

I

-X-

- ir Product

The pibonds between thedienee dienophile

interact or engage to be able to create new sigma

bonds . The 1 , 4 product is favored by the electrical

arrangement.

= Ibelieve that this inendo dueto the election with drawing group of diehophile is pointing at thei electrons of diene . I do

also thinkthat this regioisomer is chial with the chance

of being formed as an equal mixture wI two enautioners .

- HBr - A 1 I- I It knCH2C12 I

/XX 40° I -

Br minor

major 1 , 4

1 , 2

1 .2 addition product usually forms under hiretic conditions while

the 1 adduct is thermodinamically favored .

At higher temperatures ,

however , the 1 ,2 dominates over the

1 ,U-

i . achiral

This molecule is superinposable all while they are not

enantiotopic or diastereotopic, meaning replacing any of the methul group protons would not result us with

a new chiral center

This product is thermodynamic - this is shown in

now I becomes more stable o dominant at higher

temperatures .

& dehydrogenation

- -> --CrO-A1203 -

E E

11 - 1 + atebr[Ins -

HarS I

Your Name: Rosezinna Bomero 1. Consider the Diels-Alder cycloaddition reaction below and complete parts (a)-(b) below.

H

D= deuterium = ZH

heat

(a) Draw the major regioisomer (or in other words, constitutional isomer) expected to form. Also, draw appropriate resonance structures to explain why only one constitutional isomer is expected to form. Discuss the interactions between the diene and dienophile that govern this constitutional

isomer being the only one expected.

epro duct

They lone electron pairs are the Oxygen's XN eetg ay siting

C an

In th1s

In the rxN.

There is a car bonyl group

1

One

donate and add dienopnites and only realo Son er

(b) Redraw the regioisomer from part (a) and show the appropriate stereochemistry using correct dash/wedge notation expected for the major product. Discuss if this is the endo or exo diastereomer and draw a transition-state intermediate to help illustrate why this diastereomer is favored. Also, discuss if you believe this diastereomer is chiral or achiral. If it is chiral, also discuss if you think it will be formed as an equal mixture of two enantiomers (known as racemic).

H

or

D

HBr

H

100°C

A new bond Was for mod betwcen the diene and drenophile = more stable

2. Consider the reaction below and complete parts (a)-(c): (Complete a to c in the next pages)

endo diastercomer

2

chiral ’ non-Supermpos able Mirror 1maqe ot each other

(a) When the molecule below is treated with HBr at high temperatures, the 1,2-addition product predominates, rather than the 1,4-adduct. Draw this product and explain this result. Use appropriate resonance structures to illustrate.

CH3

CH3

Ct3

CH3

CH3

CH3

1,2 adduct

4

Br

CH3

CH3

CHs

CH3

(b) Indicate if this product is () achiral, (iiy chiraland racemic, or (ii) chiral, non-racemic. Discuss how you know this to be true.

Carbocation is planar

are

3

CH3

+ertiary Car bocation

Bacemic mixture

Note! a chiral has 2 similar SJbstituent

1,2 addvct

(more stable)

I,4 adduct

Note' the enantioers non-superimposed mirror

The product is chira ’ it has differet

Out of

images Substtuents.

the four.

(c) Is this product the thermodynamic product or kinetic product? Discuss what led you to this answer.

Thermodynamie product ,2-addition stable VS |,4-odd uct

en ergy has been qiven to the YxN

hegh temp. (loo* )

3. Using the carbon sources provided and any other necessary reagents needed, propose a viable synthesis for the product shown. Your synthesis must includea Diels-Alder reaction. For each step in your synthesis be sure to show the reagents/conditions necessary for that step and also draw the major product expected for each step leading to the product. You will also need to use reactions discussed in previous chapters as well.

Carbon Sources Available

H,C=CH2

CHgBr

steps

4

OH

qve cycloaddition produets brlgnard reagen+ make alchol w/ car bonyl by nucleoplicie addi

OH

Hzo

v8S is a brominatng re agent at allyhe ? Benzu)

H 25oy

<’

5

to ketone

oH

OH

LoH

Dels Aldes fxN

Ox1di2es alcohol

Br

H2O Cts mg Br

+ ||

had

Note: Pcc

NBS.

H2So4

Bth

1

Your Name: 1. Consider the Diels-Alder cycloaddition reaction below and complete parts (a)-(b) below.

(a) Draw the major regioisomer (or in other words, constitutional isomer) expected to form. Also, draw appropriate resonance structures to explain why only one constitutional isomer is expected to form. Discuss the interactions between the diene and dienophile that govern this constitutional isomer being the only one expected.

Leen Akil

0

D

weE's.gg a o o

The dienophile is the target and the diene is the attacker in this chemical process It occurs spontaneously when the temperature rises and no dddational catalyst is required The location of the new formed double bond

is

critisal to the Diels Alder process The diene's additional electrons in this reaction enable it to bind with the dineophile consider it as a giver where the diene is and the dienophile as a taker This unique configuration where the diene has a carbonyl group closeby results in the production of asingle kind of product

2

(b) Redraw the regioisomer from part (a) and show the appropriate stereochemistry using correct dash/wedge notation expected for the major product. Discuss if this is the endo or exo diastereomer and draw a transition-state intermediate to help illustrate why this diastereomer is favored. Also, discuss if you believe this diastereomer is chiral or achiral. If it is chiral, also discuss if you think it will be formed as an equal mixture of two enantiomers (known as racemic). 2. Consider the reaction below and complete parts (a)-(c): (Complete a to c in the next pages)

(a) When the molecule below is treated with HBr at high temperatures, the 1,2-addition product predominates, rather than the 1,4-adduct. Draw this product and explain this result. Use appropriate resonance structures to illustrate.

on 0 x

o

I O

Endo imaion

YMinor

TWO distinct products withdistinctshapes are produced intheDieldsAlder process calling one of thesegoodsthe endo product it is morewidely availablethantheother whilethe lesscommon isreferred to as the exo product Thearrangement oftheatoms is what causes us to obtain more oftheendoproductthe carbonylgroupsin the dienophilewhichareelectrontakers arecloserto the hydrogens in the dienewhichare similarto electron givers theendo product is preferred in this arrangment while bothproducts presentarechiralcompounds

3

(b) Indicate if this product is (i) achiral, (ii) chiral and racemic, or (iii) chiral, non-racemic. Discuss how you know this to be true.

12 Addition stable 3 carbocation

ooooo

tf no Bro ooo

Go to

113Addition

Hot n c s

pot are

unstable 2 carbocation

e 112addition is more stable

we note that the product contains a unique C atom that has theability to form many mirror image forms of the compound Because of this the resultis chiral

meaning it has a separate forms from the leftand right hands Moreover during thereaction a laubocation occurs in this molecule when a carbocation ofcurl the resorting protest usually consists of a mixture ofequal parts left and right handedforms The carbocationis a flat planar structure and the nucleophile an approachit from any side which iswhy this is rettered to as aracemic mixture in contusion the result is a racemic mixture that is chiral consisting of two distin t mirror image form that coexist in equal amounts

4

(c) Is this product the thermodynamic product or kinetic product? Discuss what led you to this answer.

3. Using the carbon sources provided and any other necessary reagents needed, propose a viable synthesis for the product shown. Your synthesis must include a Diels-Alder reaction. For each step in your synthesis be sure to show the reagents/conditions necessary for that step and also draw the major product expected for each step leading to the product. You will also need to use reactions discussed in previous chapters as well.

T temperature reactions have a tendency to favor the creation of compounds known as thermodynamic Products This is supported by the fact that th reactants have more energy at P temperatures enablingthem to go pastenergy barriers and arriveat a more stable end state The thermodynamicproduct is this stable state whim is preferred inthese circumstances due to it byenergyAs a result a product that forms at p temp is probably thermodynamic meaning it the reactionsmore stable and desired result

5

ether

nos nu g

wave

nm

µ

nu g want a t p a

mottoNBS i

1 3 o no arms at

winger

oar agnosia