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Chapter 17: Alcohols and Phenols

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Chapter 17: Alcohols and Phenols

19 problems · 39 figures

17-1 §17.1 source ↗

Give IUPAC names for the following compounds:
(a)
(b)
(c)
(d)
(e)
(f)

Answer (6 parts)

(a)
5-Methyl-2,4-hexanediol
(b)
2-Methyl-4-phenyl-2-butanol
(c)
4,4-Dimethylcyclohexanol
(d)
trans-2-Bromocyclopentanol
(e)
4-Bromo-3-methylphenol
(f)
2-Cyclopenten-1-ol

17-2 §17.1 source ↗

Draw structures corresponding to the following IUPAC names:
(a)
(Z)-2-Ethyl-2-buten-1-ol
(b)
3-Cyclohexen-1-ol
(c)
trans-3-Chlorocycloheptanol
(d)
1,4-Pentanediol
(e)
2,6-Dimethylphenol
(f)
o-(2-Hydroxyethyl)phenol

Answer (6 parts)

(a)
(b)
(c)
(d)
(e)
(f)

17-3 §17.2 source ↗

The following data for isomeric four-carbon alcohols show that there is a decrease in boiling point with increasing substitution of the OH-bearing carbon. How might you account for this trend?

• 1-Butanol, bp 117.5 °C

• 2-Butanol, bp 99.5 °C

• 2-Methyl-2-propanol, bp 82.2 °C

Answer

Hydrogen-bonding is more difficult in hindered alcohols.

17-4 §17.2 source ↗

Rank the following substances in order of increasing acidity:
(a)
(CH3)2CHOH, HC ≡ CH, (CF3)2CHOH, CH3OH
(b)
Phenol, p-methylphenol, p-(trifluoromethyl)phenol
(c)
Benzyl alcohol, phenol, p-hydroxybenzoic acid

Answer (3 parts)

(a)
HC ≡ CH < (CH3)2CHOH < CH3OH < (CF3)2CHOH
(b)
p-Methylphenol < Phenol < p-(Trifluoromethyl)phenol
(c)
Benzyl alcohol < Phenol < p-Hydroxybenzoic acid

17-5 §17.2 source ↗

p-Nitrobenzyl alcohol is more acidic than benzyl alcohol, but p-methoxybenzyl alcohol is less acidic. Explain.

Answer

The electron-withdrawing nitro group stabilizes an alkoxide ion, but the electron-donating methoxyl group destabilizes the anion.

17-6 §17.3 source ↗

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

Answer (3 parts)

(a)
2-Methyl-3-pentanol
(b)
2-Methyl-4-phenyl-2-butanol
(c)
meso-5,6-Decanediol

17-7 §17.4 source ↗

What reagent would you use to accomplish each of the following reactions?
(a)
(b)
(c)

Answer (3 parts)

(a)
NaBH4
(b)
LiAlH4
(c)
LiAlH4

17-8 §17.4 source ↗

What carbonyl compounds give the following alcohols on reduction with LiAlH4? Show all possibilities.
(a)
(b)
(c)
(d)

Answer (4 parts)

(a)
Benzaldehyde or benzoic acid (or ester)
(b)
Acetophenone
(c)
Cyclohexanone
(d)
2-Methylpropanal or 2-methylpropanoic acid (or ester)

17-9 §17.5 source ↗

Show the products obtained from addition of methylmagnesium bromide to the following compounds:
(a)
Cyclopentanone
(b)
Benzophenone (diphenyl ketone)
(c)
3-Hexanone

Answer (3 parts)

(a)
1-Methylcyclopentanol
(b)
1,1-Diphenylethanol
(c)
3-Methyl-3-hexanol

17-10 §17.5 source ↗

Use a Grignard reaction to prepare the following alcohols:
(a)
2-Methyl-2-propanol
(b)
1-Methylcyclohexanol
(c)
3-Methyl-3-pentanol
(d)
2-Phenyl-2-butanol
(e)
Benzyl alcohol
(f)
4-Methyl-1-pentanol

Answer (6 parts)

(a)
(b)
(c)
(d)
(e)
(f)

17-11 §17.5 source ↗

Use the reaction of a Grignard reagent with a carbonyl compound to synthesize the following compound:

Answer

Cyclohexanone + CH3CH2MgBr

17-12 §17.6 source ↗

How would you carry out the following transformation, a step used in the commercial synthesis of (S)-ibuprofen?

Answer

1. p-TosCl, pyridine; 2. NaCN

17-13 §17.6 source ↗

What product(s) would you expect from dehydration of the following alcohols with POCl3 in pyridine? Indicate the major product in each case.
(a)
(b)
(c)
(d)
(e)

Answer (5 parts)

(a)
2-Methyl-2-pentene
(b)
3-Methylcyclohexene
(c)
1-Methylcyclohexene
(d)
2,3-Dimethyl-2-pentene
(e)
2-Methyl-2-pentene

17-14 §17.7 source ↗

What alcohols would give the following products on oxidation?
(a)
(b)
(c)

Answer (3 parts)

(a)
1-Phenylethanol
(b)
2-Methyl-1-propanol
(c)
Cyclopentanol

17-15 §17.7 source ↗

What products would you expect from oxidation of the following compounds with chromium trioxide in hydronium? In the Dess–Martin periodinane?
(a)
1-Hexanol
(b)
2-Hexanol
(c)
Hexanal

Answer (3 parts)

(a)
Hexanoic acid, hexanal
(b)
2-Hexanone
(c)
Hexanoic acid, no reaction

17-16 §17.8 source ↗

Propose a mechanism for the reaction of cyclohexyl TMS ether with LiF to deprotect the silyl ether.

Answer

SN2 reaction of F− on silicon with displacement of alkoxide ion.

17-17 §17.9 source ↗

Show the mechanism for the reaction of p-methylphenol with 2-methylpropene and H3PO4 catalyst to yield the food additive BHT.

Answer

Protonation of 2-methylpropene gives the tert-butyl cation, which carries out an electrophilic aromatic substitution reaction.

17-18 §17.11 source ↗

Assume that you need to prepare 5-cholesten-3-one from cholesterol. How could you use IR spectroscopy to tell whether the reaction was successful? What differences would you look for in the IR spectra of starting material and product?

Answer

Disappearance of –OH absorption; appearance of C = O

17-19 §17.11 source ↗

When the 1H NMR spectrum of an alcohol is run in dimethyl sulfoxide (DMSO) solvent rather than in chloroform, exchange of the O–H proton is slow and spin–spin splitting is seen between the O–H proton and C–H protons on the adjacent carbon. What spin multiplicities would you expect for the hydroxyl protons in the following alcohols?
(a)
2-Methyl-2-propanol
(b)
Cyclohexanol
(c)
Ethanol
(d)
2-Propanol
(e)
Cholesterol
(f)
1-Methylcyclohexanol

Answer (6 parts)

(a)
Singlet
(b)
Doublet
(c)
Triplet
(d)
Doublet
(e)
Doublet
(f)
Singlet

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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.