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Chapter 18: Ethers and Epoxides; Thiols and Sulfides

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Chapter 18: Ethers and Epoxides; Thiols and Sulfides

21 problems · 40 figures

18-1 §18.1 source ↗

Name the following ethers:
(a)
(b)
(c)
(d)
(e)
(f)

Answer (6 parts)

(a)
Diisopropyl ether
(b)
Cyclopentyl propyl ether
(c)
p-Bromoanisole or 4-bromo-1-methoxybenzene
(d)
1-Methoxycyclohexene
(e)
Ethyl isobutyl ether
(f)
Allyl vinyl ether

18-2 §18.2 source ↗

Why do you suppose only symmetrical ethers are prepared by the sulfuric-acid-catalyzed dehydration procedure? What product(s) would you expect if ethanol and 1-propanol were allowed to react together? In what ratio would the products be formed if the two alcohols were of equal reactivity?

Answer

A mixture of diethyl ether, dipropyl ether, and ethyl propyl ether is formed in a 1 : 1 : 2 ratio.

18-3 §18.2 source ↗

How would you prepare the following ethers using a Williamson synthesis?
(a)
Methyl propyl ether
(b)
Anisole (methyl phenyl ether)
(c)
Benzyl isopropyl ether
(d)
Ethyl 2,2-dimethylpropyl ether

Answer (4 parts)

(a)
CH3CH2CH2O− + CH3Br
(b)
PhO− + CH3Br
(c)
(CH3)2CHO− + PhCH2Br
(d)
(CH3)3CCH2O− + CH3CH2Br

18-4 §18.2 source ↗

Review the mechanism of oxymercuration shown in Figure 8.4, and then write the mechanism of the alkoxymercuration reaction of 1-methylcyclopentene with ethanol. Use curved arrows to show the electron flow in each step.
Figure 8.4 in the book ↗

Answer

18-5 §18.2 source ↗

How would you prepare the following ethers? Use whichever method you think is more appropriate, Williamson synthesis or the alkoxymercuration reaction.
(a)
Butyl cyclohexyl ether
(b)
Benzyl ethyl ether (C6H5CH2OCH2CH3)
(c)
sec-Butyl tert-butyl ether
(d)
Tetrahydrofuran

Answer (4 parts)

(a)
Either method
(b)
Williamson
(c)
Alkoxymercuration
(d)
Williamson

18-6 §18.2 source ↗

Rank the following halides in order of their reactivity in the Williamson synthesis:
(a)
Bromoethane, 2-bromopropane, bromobenzene
(b)
Chloroethane, bromoethane, 1-Iodopropene

Answer (2 parts)

(a)
Bromoethane > 2-Bromopropane > Bromobenzene
(b)
Bromoethane > Chloroethane > 1-Iodopropene

18-7 §18.3 source ↗

Predict the products of the following reactions:
(a)
(b)

Answer (2 parts)

(a)
(b)

18-8 §18.3 source ↗

Write the mechanism of the acid-induced cleavage of tert-butyl cyclohexyl ether to yield cyclohexanol and 2-methylpropene.

Answer

Protonation of the oxygen atom, followed by E1 reaction

18-9 §18.3 source ↗

Why are HI and HBr more effective than HCl in cleaving ethers? (See Section 11.3.)

Answer

Br− and I− are better nucleophiles than Cl−.

18-10 §18.4 source ↗

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

Answer

18-11 §18.4 source ↗

Reaction of cis-2-butene with m-chloroperoxybenzoic acid yields an epoxide different from that obtained by reaction of the trans isomer. Explain.

Answer

Epoxidation of cis-2-butene yields cis-2,3-epoxybutane, while epoxidation of trans-2-butene yields trans-2,3-epoxybutane.

18-12 §18.5 source ↗

Predict the major product of each of the following reactions:
(a)
(b)

Answer (2 parts)

(a)
(b)

18-13 §18.5 source ↗

How would you prepare the following diols?
(a)
(b)

Answer (2 parts)

(a)
1-Methylcyclohexene + OsO4; then NaHSO3
(b)
1-Methylcyclohexene + m-chloroperoxybenzoic acid, then H3O+

18-14 §18.5 source ↗

Predict the major product of the following reactions:
(a)
(b)
(c)

Answer (3 parts)

(a)
(b)
(c)

18-15 §18.6 source ↗

15-Crown-5 and 12-crown-4 ethers complex Na+ and Li+, respectively. Make models of these crown ethers, and compare the sizes of the cavities.

Answer

18-16 §18.7 source ↗

Name the following compounds:
(a)
(b)
(c)
(d)
(e)
(f)

Answer (6 parts)

(a)
2-Butanethiol
(b)
2,2,6-Trimethyl-4-heptanethiol
(c)
2-Cyclopentene-1-thiol
(d)
Ethyl isopropyl sulfide
(e)
o-Di(methylthio)benzene
(f)
3-(Ethylthio)cyclohexanone

18-17 §18.7 source ↗

2-Butene-1-thiol is one component of skunk spray. How would you synthesize this substance (either cis or trans) from methyl 2-butenoate? From 1,3-butadiene?

Answer

• (a) 1. LiAlH4; 2. PBr3; 3. ( H 2 N ) 2 C ═ S ; 4. H2O, NaOH

• (b) 1. HBr; 2. ( H 2 N ) 2 C ═ S ; 3. H2O, NaOH

18-18 §18.8 source ↗

The 1H NMR spectrum shown is that of a cyclic ether with the formula C4H8O. Propose a structure.

Answer

1,2-Epoxybutane

18-69 Preview of Carbonyl Chemistry source ↗

Judging from the following electrostatic potential maps, which kind of carbonyl compound has the more electrophilic carbonyl carbon atom, a ketone or an acid chloride? Which has the more nucleophilic carbonyl oxygen atom? Explain.

Answer

Acetyl chloride is more electrophilic than acetone.

18-70 Preview of Carbonyl Chemistry source ↗

Predict the product formed by nucleophilic addition of cyanide ion (CN–) to the carbonyl group of acetone, followed by protonation to give an alcohol:

Answer

18-71 Preview of Carbonyl Chemistry source ↗

Identify each of the following reactions as a nucleophilic addition, nucleophilic acyl substitution, an α substitution, or a carbonyl condensation:
(a)
(b)
(c)

Answer (3 parts)

(a)
Nucleophilic acyl substitution
(b)
Nucleophilic addition
(c)
Carbonyl condensation

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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.