Answer Key Chemistry 233 Chapter 11 Problem Set – Pt. 2 ...

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Chemistry233Chapter11ProblemSet–Pt.2(EliminationReactions)

1. TheexamplebelowwasgivenontheCh.9ProblemSet.Givenwhatyounowknow,whatproduct(s)

wouldyouexpecttoisolatefromthisreaction?

2. SpecifyhoweachofthefollowingwouldaffecttherateofanE2reaction.

a. IncreasechangingthebasefromNaOCH3toNaNH2.

b. Increasingtheconcentrationofbase.

c. Decreasingtheconcentrationofalkylhalide.

d. Changingthealkyhalidefrom2-bromo-2-ethylpentaneto2-bromopentane.

e. Changingthealkylhalidefrom2-bromopentaneto2-iodopentane.

3. SpecifyhoweachofthefollowingwouldaffecttherateofanE1reaction.

a. ChangingthebasefromNaOHtoH2O.

b. Decreasingtheconcentrationofbase.

c. Changingthesolventfromacetonetomethanol.

d. Changingthealkyhalidefrom2-bromo-2-ethylpentaneto2-bromopentane.4. Predicttheproduct(s)foreachoftheE2eliminationreactionsbelow.Identifythemajorproductfor

each.

Br+ ONa

(NaOt-Bu)

No Substitution Reaction

Br

Ph

Cl

Br

BrO

KOHHeat

NaOCH3

Heat

HeatO

a.

b.

c.

d.

BulkybasegivestheHofmannElimination productHRnfl 8tBu

rtGbrE2 Rate KCRX Base

Trate Nolte is a strongerbasethan 8dBT rate

to rateBryEt Brf rate Ezra letwithsubstitution 30Br 1 20Br

T rate TbetterLGEl Rate k Rx

Nocharge

No change

T rate Tpoleraprotic C polarProtic

Irate El rate with substitution

YT Zaitsev

Rotateso 49 Hectare 4 pf antiperiplosar

p No Rtn No BH

HofmannProduct

Answer Key

Chem.233–Chapter11-Pt.2ProblemSet

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5. Showthecompleteelectronpushingmechanismforthereactioninquestion4parta.

6. Predicttheproduct(s)foreachoftheE1eliminationreactionsbelow.Identifythemajorproductforeach.

7. Showthecompleteelectronpushingmechanismforthereactioninquestion6partc.

8. Foreachreactionbelow,predicttheE2eliminationproductwithcorrectalkenestereochemistrywhereappropriate.Also,drawthereactive(anti-periplanar)conformation.

9. Thecompoundbelowcanundergotwosuccessiveeliminationreactionsuponheating.Drawtheproductofthereaction.

Br

I

Br

H2OHeat

CH3OHHeat

CH3OHHeat

a.

b.

c.

a.

b.

Cl

PhNaOEtHeat

IEt

NaNH2Heat

PhCl

ClNaNH2DMF

YI t Ho t Bro2

my

Tu

E

ph pht b Phat t lhotoats

t B

o i Him

µqg ph zt8k Ph

Chem.233–Chapter11-Pt.2ProblemSet

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10. Circletheoneineachofthefollowingpairsthatwouldbeexpectedtogiveahigheryieldofeliminationoversubstitution.

11. Synthesis:Proposeasynthesisforeachofthefollowingstartingwith2-bromobutane.

a. 2-butene

b. 2-butyne

c. 2-butanold. butane

12. Rankthefollowingfromfastest(1)toslowest(4)E2elimination.

II + NaOH+ NaOH

Cl + KO Cl + KO

Br+ CH3O

Br+ CH3O

Low T High T

vs

vs

vs

a.

b.

c.

Br BrBr Br

zo faster E2Slower Snz Vs 10

Bulky base Cer onlydo elimination

High T favorselimination

Br or other small base1 a

or other baseF NENE See Q9Br nao 8 NIH1

Br N t1

A BC D

sina.inB H access reactiveconformation