← Back

Chapter 8: Alkenes: Reactions and Synthesis

Every problem in the chapter beside the book’s answer, a chapter at a time as you scroll.

Chapter 8: Alkenes: Reactions and Synthesis

21 problems · 31 figures

8-1 §8.1 source ↗

One problem with elimination reactions is that mixtures of products are often formed. For example, treatment of 2-bromo-2-methylbutane with KOH in ethanol yields a mixture of two alkene products. What are their likely structures?

Answer

2-Methyl-2-butene and 2-methyl-1-butene

8-2 §8.1 source ↗

How many alkene products, including E,Z isomers, might be obtained by dehydration of 3-methyl-3-hexanol with aqueous sulfuric acid?

Answer

Five

8-3 §8.2 source ↗

What product would you expect to obtain from addition of Cl2 to 1,2-dimethylcyclohexene? Show the stereochemistry of the product.

Answer

trans-1,2-Dichloro-1,2-dimethylcyclohexane

8-4 §8.2 source ↗

Addition of HCl to 1,2-dimethylcyclohexene yields a mixture of two products. Show the stereochemistry of each, and explain why a mixture is formed.

Answer

8-5 §8.3 source ↗

What product would you expect from the reaction of cyclopentene with NBS and water? Show the stereochemistry.

Answer

trans-2-Bromocyclopentanol

8-6 §8.3 source ↗

When an unsymmetrical alkene such as propene is treated with N-bromosuccinimide in aqueous dimethyl sulfoxide, the major product has the bromine atom bonded to the less highly substituted carbon atom. Is this Markovnikov or non-Markovnikov orientation? (Section 7.8) Explain.

Answer

Markovnikov

8-7 §8.4 source ↗

What products would you expect from oxymercuration–demercuration of the following alkenes?
(a)
(b)

Answer (2 parts)

(a)
2-Pentanol
(b)
2-Methyl-2-pentanol

8-8 §8.4 source ↗

From what alkenes might the following alcohols have been prepared?
(a)
(b)

Answer (2 parts)

(a)
Oxymercuration of 2-methyl-1-hexene or 2-methyl-2-hexene
(b)
Oxymercuration of cyclohexylethylene or hydroboration of ethylidenecyclohexane

8-9 §8.5 source ↗

Show the structures of the products you would obtain by hydroboration–oxidation of the following alkenes:
(a)
(b)

Answer (2 parts)

(a)
(b)

8-10 §8.5 source ↗

What alkenes might be used to prepare the following alcohols by hydroboration–oxidation?
(a)
(b)
(c)

Answer (3 parts)

(a)
3-Methyl-1-butene
(b)
2-Methyl-2-butene
(c)
Methylenecyclohexane

8-11 §8.5 source ↗

The following cycloalkene gives a mixture of two alcohols on hydroboration followed by oxidation. Draw the structures of both, and explain the result.

Answer

8-12 §8.6 source ↗

What product would you obtain from catalytic hydrogenation of the following alkenes?
(a)
(b)
(c)

Answer (3 parts)

(a)
2-Methylpentane
(b)
1,1-Dimethylcyclopentane
(c)
tert-Butylcyclohexane

8-13 §8.7 source ↗

What product would you expect from reaction of cis-2-butene with meta-chloroperoxybenzoic acid? Show the stereochemistry.

Answer

8-14 §8.7 source ↗

Starting with an alkene, how would you prepare each of the following compounds?
(a)
(b)
(c)

Answer (3 parts)

(a)
1-Methylcyclohexene
(b)
2-Methyl-2-pentene
(c)
1,3-Butadiene

8-15 §8.8 source ↗

What products would you expect from reaction of 1-methylcyclohexene with the following reagents?
(a)
Aqueous acidic KMnO4
(b)
O3, followed by Zn, CH3CO2H

Answer (2 parts)

(a)
CH3COCH2CH2CH2CH2CO2H
(b)
CH3COCH2CH2CH2CH2CHO

8-16 §8.8 source ↗

Propose structures for alkenes that yield the following products on reaction with ozone followed by treatment with Zn:
(a)
(CH3)2C = O + H2C = O
(b)
2 equiv CH3CH2CH = O

Answer (2 parts)

(a)
2-Methylpropene
(b)
3-Hexene

8-17 §8.9 source ↗

What products would you expect from the following reactions?
(a)
(b)

Answer (2 parts)

(a)
(b)

8-18 §8.10 source ↗

Show the monomer units you would use to prepare the following polymers:
(a)
(b)

Answer (2 parts)

(a)
H2C ═ CHOCH3
(b)
ClCH ═ CHCl

8-19 §8.10 source ↗

One of the chain-termination steps that sometimes occurs to interrupt polymerization is the following reaction between two radicals. Propose a mechanism for the reaction, using fishhook arrows to indicate electron flow.

Answer

8-20 §8.13 source ↗

What products are formed from acid-catalyzed hydration of racemic (±)-4-methyl-1-hexene? What can you say about the relative amounts of the products? Is the product mixture optically active?

Answer

An optically inactive, non-50 : 50 mixture of two racemic pairs: (2R,4R) + (2S,4S) and (2R,4S) + (2S,4R)

8-21 §8.13 source ↗

What products are formed from hydration of 4-methylcyclopentene? What can you say about the relative amounts of the products?

Answer

Non-50 : 50 mixture of two racemic pairs: (1S,3R) + (1R,3S) and (1S,3S) + (1R,3R)

Loading chapter 9…

Problems and answers are adapted from Organic Chemistry: A Tenth Edition by John McMurry, OpenStax, and are used under the CC BY-NC-SA 4.0 licence. Access for free at https://openstax.org/books/organic-chemistry/pages/1-why-this-chapter. Illustrations: Copyright Rice University, OpenStax, under CC BY-NC-SA 4.0 license. This adaptation is released under the same licence, is non-commercial, and is neither affiliated with nor endorsed by OpenStax or Rice University.