Chapter 8

Question 1

HBr can be added to an alkene in the presence of peroxides (ROOR). What function does the peroxide serve in this reaction?

A) nucleophile
B) electrophile
C) radical chain initiator
D) acid catalyst
E) solvent

Answer 1

C) radical chain initiator

Question 2

Name the major product which results when HBr is added to 3-ethyl-3-hexene.

Answer 2

3-bromo-3-ethylhexane

Question 3

The mechanism for the acid-catalyzed hydration of alkenes is simply the reverse of the mechanism by which alcohols are dehydrated using concentrated acid. This is an illustration of the principle of ________.

Answer 3

microscopic reversibility

Question 4

Name the major alcohol product which results when 3,3-dimethylbut-1-ene is treated with dilute acid.

Answer 4

2,3-dimethyl-2-butanol

Question 5

Which of the following intermediates is thought to occur in the mechanism by which alkenes are hydrated in the presence of acid?

A) carbanion
B) carbocation
C) free radical
D) carbene
E) alkyne

Answer 5

B) carbocation

Question 6

Which of the following is the best reaction sequence to use if one wants to accomplish a Markovnikov addition of water to an alkene with minimal skeletal rearrangement?

A) water + dilute acid
B) water + concentrated acid
C) oxymercuration-demercuration
D) hydroboration-oxidation
E) none of the above

Answer 6

C) oxymercuration-demercuration

Question 7

What synthetic goal is achieved by subjecting an alkene to an oxymercuration-demercuration sequence?

A) Markovnikov addition of H2O wherein skeletal rearrangement is promoted
B) Markovnikov addition of H2O wherein skeletal rearrangement is prevented
C) anti-Markovnikov addition of H2O wherein skeletal rearrangement is promoted
D) anti-Markovnikov addition of H2O wherein skeletal rearrangement is prevented
E) syn-hydroxylation

Answer 7

B) Markovnikov addition of H2O wherein skeletal rearrangement is prevented

Question 8

When an alkene is subjected to treatment with Hg(OAc)2 in alcohol followed by reaction with NaBH4, what new class of compound is formed?

A) ether
B) epoxide
C) alkane
D) syn diol
E) alkyne

Answer 8

A) ether

Question 9

Treatment of 2-methylpropene with which of the following reaction conditions results in an anti- Markovnikov addition product?

A) dry gaseous HBr with peroxides present
B) BH3-THF, followed by alkaline H2O2
C) aqueous Hg(OAc)2, followed by alkaline NaBH4
D) dilute H2SO4 and heat
E) both A and B

Answer 9

E) both A and B

Question 10

50) Both (E)- and (Z)-hex-3-ene can be subjected to a hydroboration-oxidation sequence. How are the products from these two reactions related to each other?

A) The (E)- and (Z)-isomers generate the same products but in differing amounts.
B) The (E)- and (Z)-isomers generate the same products in exactly the same amounts.
C) The products of the two isomers are related as constitutional isomers.
D) The products of the two isomers are related as diastereomers.
E) The products of the two isomers are not structurally related.

Answer 10

B) The (E)- and (Z)-isomers generate the same products in exactly the same amounts.

Question 11

Which of the following additions to alkenes occur(s) specifically in an anti fashion?

A) hydroboration-oxidation
B) addition of Br2
C) addition of H2
D) addition of H2O in dilute acid
E) both A and B

Answer 11

B) addition of Br2

Question 12

64) Addition of Br2 to (E)-hex-3-ene produces ________.

A) a meso dibromide
B) a mixture of enantiomeric dibromides which is optically active
C) a mixture of enantiomeric dibromides which is optically inactive
D) (Z)-3,4-dibromo-3-hexene
E) (E)-3,4-dibromo-3-hexene

Answer 12

A) a meso dibromide

Question 13

Both (E)- and (Z)-hex-3-ene can be treated with D2 in the presence of a platinum catalyst. How are the products from these two reactions related to each other?

A) The (E)- and (Z)-isomers generate the same products but in differing amounts.
B) The (E)- and (Z)-isomers generate the same products in exactly the same amounts.
C) The products of the two isomers are related as constitutional isomers.
D) The products of the two isomers are related as diastereomers.
E) The products of the two isomers are related as enantiomers.

Answer 13

D) The products of the two isomers are related as diastereomers.

Question 14

________ is the use of an optically active reagent or catalyst to convert an optically inactive starting material into an optically active product.

A) Asymmetric induction
B) Racemization
C) Optical reduction
D) Meso effection
E) Chiralization

Answer 14

A) Asymmetric induction

Question 15

Treatment of cyclopentene with peroxybenzoic acid ________.

A) results in oxidative cleavage of the ring to produce an acyclic compound
B) yields a meso epoxide
C) yields an equimolar mixture of enantiomeric epoxides
D) gives the same product as treatment of cyclopentene with OsO4
E) none of the above

Answer 15

B) yields a meso epoxide

Question 16

A reaction of an unknown alkene with MCPBA in dichloromethane followed by work-up with H2O/H+ yielded, as the major product, a racemic mixture of (2S, 3S) and (2R, 3R)-3-methylpentan-2,3-diol. What is the specific structure of the alkene used in the reaction?

A) (Z)-3-methylpent-2-ene
B) (E)-3-methylpent- 2-ene
C) 2-methylpent-2-ene
D) 2,3-dimethylbut-2-ene
E) none of the above

Answer 16

A) (Z)-3-methylpent-2-ene

Question 17

Which of the following additions to alkenes occur(s) specifically in an syn fashion?

A) dihydroxylation using OsO4, H2O2
B) addition of H2
C) hydroboration
D) addition of HCl
E) A, B, and C

Answer 17

E) A, B, and C

Question 18

Which of the following compounds is (are) appropriate to promote the cationic polymerization of isobutylene?

A) H2SO4
B) BF3
C) ROOR
D) NaOH
E) both H2SO4 and BF3

Answer 18

E) both H2SO4 and BF3

Question 19

Which of the following compounds is (are) appropriate to promote the cationic polymerization of isobutylene?

A) H2SO4
B) BF3
C) ROOR
D) NaOH
E) both H2SO4 and BF3

Answer 19

E) both H2SO4 and BF3

Question 20

Ozonolysis-reduction of an unknown alkene gives equal amounts of CH3CH2CHO and CH3CH2CH2CHO. Name the unknown alkene.

Answer 20

Either (E)- or (Z)-3-heptene

Question 21

What alkene, which contains no oxygen atoms and a single CC, will give CH3CO(CH2)4CHO upon treatment with OsO4 followed by cleavage with periodic acid?

Answer 21

1-methylcyclohexene

Question 22

What cyclic products results when 1,8-nonadiene is treated with Grubbs catalyst?

Answer 22

cycloheptene