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C H A P T E R 2 2

ALCOHOLS, ETHERS, PHENOLS, AND THIOLS

SOLUTIONS TO REVIEW QUESTIONS

1. The question allows great freedom of choice. These shown here are very simple examples of each type.

(a) an alkyl halide CH3CH2Cl

(b) a phenol OH

(c) an ether CH3CH2OCH2CH3

(d)

(e)

(f) a carboxylic acid CH3COOH

(g)

(h) a thiol CH3CH2SH

2. Alkenes are almost never made from alcohols because the alcohols are almost always the higher value

material. This is because recovering alkenes from hydrocarbon sources in an oil refinery (primarily

catalytic cracking) is a relatively cheap process.

3. Oxidation of primary alcohols yields aldehydes. Further oxidation yields carboxylic acids. Examples:

4. 1,2-Ethanediol is superior to methanol as an antifreeze because of its low volatility. Methanol is much

more volatile than water. If the radiator leaks gas under pressure (normally steam), it would primarily

leak methanol vapor so you would soon have no antifreeze. Ethylene glycol has a lower volatility than

water, so it does not present this problem.

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5. Oxidation of alcohols affects the hydroxyl carbon in two ways: (1) the carbon adds a new bond to

oxygen; (2) the carbon loses a bond to hydrogen. When the hydroxyl carbon is not directly bonded to

hydrogen (as in tertiary alcohols), oxidation is difficult.

6. Dietary polyphenols have a variety of health benefits. They protect cells from oxidation by acting as

antioxidants. Perhaps more importantly polyphenols can serve as cellular signaling compounds. They

can decrease the risk of coronary heart disease by impacting arterial cells. By interacting with brain

cells, polyphenols can decrease cognitive loss. Current research suggests that polyphenols have a

beneficial impact on many cell types.

7. The liver oxidizes ingested methanol, first to methanal (formaldehyde) and then to methanoic acid

(formic acid). Methanoic acid is much more toxic than methanol. This acid causes metabolic acidosis

and inhibition of central energy metabolism that can lead to death.

8. The following classes of organic compounds can be easily formed from alcohols: aldehydes, ketones,

and carboxylic acids by oxidation; alkenes and ethers by dehydration; esters by esterification.

9.

10. Some common phenols include (a) hydroquinone, a photographic reducer and developer, (b) vanillin, a

flavoring, (c) eugenol, used to make artificial vanillin, (d) thymol, used as an antiseptic in mouthwashes,

(e) butylated hydroxytoluene (BHT), an antioxidant, and, (f) the cresols, used as disinfectants.

11. Low molar mass ethers present two hazards. They are very volatile and their highly flammable vapors

form explosive mixtures with air. They also slowly react with oxygen in the air to form unstable

explosive peroxides.

12. Ethanol (molar mass¼ 46.07) is a liquid at room temperature because it has a significant amount of

hydrogen bonding between molecules in the liquid state, and thus has a much higher boiling point than

would be predicted from molar mass alone. Dimethyl ether (molar mass¼ 46.07) is not capable of

hydrogen bonding to itself, so has low attraction between molecules, making it a gas at room

temperature.

13. Alcohols form strong intermolecular hydrogen bonds while thiols do not. Ethanol hydrogen bonding

makes for a higher boiling point than that for ethanethiol which does not hydrogen bond.

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14. At the boiling point of diethyl ether (35�C) the vapor pressure of diethyl ether must equal the

atmospheric pressure.

15. Benzyl alcohol is a primary alcohol. It can be oxidized to form an aldehyde or a carboxylic acid.

CH2OH

[O]

[O]

CH

COH

O

O

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SOLUTIONS TO EXERCISES

1. (a)

CH3CHCH3

OH (d)

CH3 C CHCHCH2 3

CH3 CH3

OH

(b)

CH2

CH

CH2 OH

OH

OH(e)

OH

(c)

CH3 CHCHCH2 2 OHCHCH 2

CH3 CH3(f) CH3CH2OH

2. (a)OH

(d) CH3CHCH2CH2OH

OH

(b) CH3CCH2CH3

OH

CH3

(e)

CH2

CH

CH2 OH

OH

OH

(c) CH3 CHCHC 2CH2CH3

CH3

CH3

OH

(f) CH3 CCHC 2CH3

OH

CH3

CH3

CH3

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3. There are only five isomers:

CH3 CHCCH 22 OH

CH3

CH3

CH2CH3 CCH2OH

CH3

CH33

CH3CHCHCH2OH

CH3

CH3

CH3CHCCH3

H C 3

CH3

OH

CH3CHCCH

CH3

CH

3

HO

4. There are only eight isomers:

CH3 CHCCH 2 CH32

CH3

OH

CH3CHCHCH2CH3

CH3

OH

CH3 CCH2CH3CH2

CH3

OH

CH3CHCHCH2CH3

CH3

OH

CH 22 CHCH CH 2CH3

CH3

HO

CH2 CHCHCH 2CH3

CH3

HO

CH3 CHCHCHCH 32

CH3 OH

2

CH3 CHCHCH 2CH2

CH3

OH2

5. (a) primary alcohols (where the hydroxyl carbon is bonded to one other carbon): b, c, f;

(b) secondary alcohols (where the hydroxyl carbon is bonded to two other carbons): a, b, e;

(c) tertiary alcohols (where the hydroxyl carbon is bonded to three other carbons): d; diol (where the

compound contains two hydroxyl groups): none; triols (where the compound contains three hydroxyl

groups): b.

6. (a) primary alcohols (where the hydroxyl carbon is bonded to one other carbon): d, e;

(b) secondary alcohols (where the hydroxyl carbon is bonded to two other carbons): a, c, d, e;

(c) tertiary alcohols (where the hydroxyl carbon is bonded to three other carbons): b, f; diol (where the

compound contains two hydroxyl groups): d; triols (where the compound contains three hydroxyl

groups): e.

7. The names of the compounds are:(a) 1-butanol (butyl alcohol) (e) 2-methyl-2-butanol

(b) 2-propanol (isopropyl alcohol) (f) 2-methylcyclohexanol

(c) 2-methyl-3-phenyl-l-propanol (g) 2,3-dimethyl-1,4-butanediol

(d) oxirane (ethylene oxide)

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8. The names of the compounds are(a) ethanol (ethyl alcohol) (e) 3-pentanol

(b) 2-phenylethanol (f) 1,2-propanediol

(c) 3-methyl-3-pentanol (g) 4-ethyl-2-hexanol

(d) 1-methylcyclopentanol

9. Chief product of dehydration

(a)

(b) CH3CH����CHCH2CH3 2-pentene

(c) cyclohexene

10. Chief product of dehydration

(a)1-methylcyclopenteneCH3

(b) CH3CH����CHCH3 2�butene

(c)

11. (a)OH

cyclopentanol

(c) OH

CH3

1-methylcyclohexanol

(b) CH3 CH2 CHCH OH2

CH3

2-methyl-1-butanol

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12. (a) CH3

CH

OH

3

1,2-dimethylcyclohexanol

(c)

CH3CH2CHCH2CH3

OH

3-pentanol

(b)

HO

4,4-dimethy1-1pentanol

CH3

CHC 3

CH3

CH2CH2CH2

13. Primary alcohols oxidize to carboxylic acids; secondary alcohols oxidize to ketones; tertiary alcohols

don’t easily oxidize.

(a)

CH3CCH2CH3

O

butanone

(b) HOOCCH2CHCH2CH3

CH2CH3

3-ethylpentanoic acid

(c)CH3CCH3

O

acetone, propanone

(d) NR

14. Primary alcohols oxidize to carboxylic acids; secondary alcohols oxidize to ketones; tertiary alcohols

don’t easily oxidize.

(a) HCOOH, methanoic acid, formic acid

(b) NR

(c) CH3COOH, ethanoic acid, acetic acid

(d)CH3CH2CCH 2CH2CH3

O

3-hexanone

15. Upon ester hydrolysis, the alcohol forms from the alkyl group and oxygen bonded to the C����O.

(a) CH3CH2CH2OH 1�butanol(b) CH3CH2OH ethanol

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(c)

CH3CHCH3

OH

2-propanol

16. Upon ester hydrolysis, the alcohol forms from the alkyl group and oxygen bonded to the C����O.

(a) OH cyclopentanol

(b) CHHO 2 CH

CH3

CH3 2-methyl-1-propanol

(c) CH3OH methanol

17. (a) CH3CHBrCH3 2-bromopropane

(b) bromocyclohexane (cyclohexyl bromide)Br

(c)

18. (a)

(b)

(c)

19. (a) 2 CH3CH2OHþ H2SO4����!140�CCH3CH2OCH2CH3 þ H2O

diethyl ether

(b) CH3CH2CH2OHþ H2SO4 ����!180�CCH3CH����CH2

propene

þH2O

(c)

(d)

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20. (a) 2 CH3CH2OHþ 2 Na����! 2 CH3CH2O�Naþ þ H2

(b)

(c)

(d)

21. (a)

(b)

(c)

22. (a) methanol, CH3��OH

(b)

(c)

23. (a) methanol

(b) 2-methyl-1-propanol

(c) cyclohexanol

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24. (a) cyclopentanol

(b) 2-propanol

(c) 2-methyl-2-propanol

25. (a) o-methylphenol

CH3

OH

(b) m-dihydroxybenzene

OH

OH

(c)

26. (a) p-nitrophenol

NO2

OH

(b) 2,6-dimethylphenol

OHCH3H3C

(c) o-dihydroxybenzene

OH

OH

27. (a) phenol (c) 2-ethyl-5-nitrophenol

(b) m-methylphenol (d) 4-bromo-2-chlorophenol

28. (a) p-dihydroxybenzene (hydroquinone) (c) 2,4-dinitrophenol

(b) 2,4-dimethylphenol (d) m-hexylphenol

29. Order of increasing solubility in water [c (lowest), a, b, d (highest)]

(c) CH3CH2CH2CH2CH3 ð1Þ (b) CH3CHðOHÞCH2CH2CH3 ð3Þ(a) CH3CH2OCH2CH2CH3 ð2Þ (d) CH3CHðOHÞCHðOHÞCH2CH3 ð4Þ

30. Order of decreasing solubility in water: [a (highest), d, c, b (lowest)]

(a) CH3CHðOHÞCHðOHÞCH2OH ð1Þ (c) CH3CH2CH2CH2OH ð3Þ(d) CH3CHðOHÞCH2CH2OH ð2Þ (b) CH3CH2OCH2CH3 ð4Þ

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31. The three compounds have about the same molar mass but differ with respect to hydrogen bonding and

polarity. Compound (b) (1-propanethiol) does not hydrogen bond, is nonpolar, and so, has the lowest

boiling point. Compound (c) (diethyl ether) is polar but does not hydrogen bond to itself. It has a higher

boiling point than compound (b). Compound a (1,2-propanediol) hydrogen bonds to itself and has the

highest boiling point.

32. The three compounds have about the same molar mass but differ with respect to hydrogen bonding and

polarity. Compound (c) (pentane) does not hydrogen bond, is nonpolar, and so, has the lowest boiling point.

Compound (b) (diethyl ether) is polar but does not hydrogen bond to itself. It has a higher boiling point than

Compound (c). Compound (a) (2-butanol) hydrogen bonds to itself and has the highest boiling point.

33. CH3��O��CH2CH3

ethyl methyl ether

CH3CH2CH2��OH

1� propanol

Each of these molecules has about the same molar mass. In this case, differences in boiling point arise

because of differences in intermolecular attractive forces. 1-propanol can hydrogen bond to itself

while ethyl methyl ether can not. Thus, ethyl methyl ether will have the lower boiling point.

boiling point for ethyl methyl ether¼ 8�Cboiling point for 1-propanol¼ 97.4� C

34.

CH3CH2 O CHCH 3

ethyl isopropyl ether

OHCH3CH2CH2CH2CH2

1-pentanol

CH3

Each of these molecules has about the same molar mass. In this case, differences in boiling point arise

because of differences in intermolecular attractive forces. 1-pentanol can hydrogen bond to itself while

ethyl isopropyl ether cannot. Thus, ethyl isopropyl ether will have the lower boiling point.

boiling point for ethyl isopropyl ether¼ 54�Cboiling point for 1-pentanol¼ 138�C

35. (a) common, isopropyl methyl ether; IUPAC, 2-methoxypropane

(b) common, ethyl phenyl ether; IUPAC, ethoxybenzene

(c) common, butyl ethyl ether; IUPAC, 1-ethoxybutane

36. (a) common, ethyl methyl ether; IUPAC, methoxyethane

(b) common, ethyl isobutyl ether; IUPAC, l-ethoxy-2-methylpropane

(c) common, ethyl phenyl ether; IUPAC, ethoxybenzene

37. There are three isomeric saturated ethers with the formula, C4H10O.

CH3 O CH2CH2CH3 CH3CH2 O CH2CH3 CH3 O CHCH 3

CH3

methyl propyl ether(1-methoxypropane)

diethyl ether(ethoxyethane)

methyl isopropyl ether(2-methoxypropane)

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38. Six isomeric ethers: C5H12O

CH3OCH2CH2CH2CH3

n-butyl methyl ether

(1-methoxybutane)

CH3CH2OCH2CH2CH3

ethyl n-propyl ether

(1-ethoxypropane)

39. Possible combinations of reactants to make the following ethers by the Williamson synthesis:

(a) CH3CH2OCH3 CH3ONaþ CH3CH2Cl or

CH3CH2ONaþ CH3Cl

(b)

or

CH2ONa± CH3CH2Cl

CH2Cl± CH3CH2ONa

CH2OCH2CH3

(c)

40. Possible combinations of reactants to make the following ethers by the Williamson synthesis:

(a) CH3CH2CH2OCH2CH2CH3 CH3CH2CH2ONaþ CH3CH2CH2Cl

(b)

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(c)

cannot be made by the Williamson synthesis. Cannot use secondary RX.

41. IUPAC names

(a) 2-methyl-2-butanethiol

(b) cyclohexanethiol

(c) 2-methyl-2-propanethiol

(d) 2-methyl-3-pentanethiol

42. IUPAC names

(a) 2-methylcyclopentanethiol

(b) 2,3-dimethyl-2-pentanethiol

(c) 2-propanethiol

(d) 3-ethyl-2,2,4-trimethyl-3-pentanethiol

43. 4-hexylresorcinol or 4-hexyl-1,3-dihydroxybenzeneOH

CH2(CH2)4CH3

OH

44.

cis-1,2-cyclopentanediolOH OH

OH

OHtrans-1,2-cyclopentanediol

45. The phenol compound (3-methylphenol) is more acidic than the alcohol compound (benzyl alcohol) but

is less acidic than carbonic acid.

46. The name “catecholamine” is built of two pieces, “catechol” and “amine.” A catechol is a phenol

derivative that contains an additional hydroxyl group (o-hydroxyphenol).

OH

OH

(An amine is a “–NH2” functional group.)

H2N

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47. Oxidation products from ethylene glycol include

HOCH2 CH

O

CHHC

OO

HOCH2COOH HOOCCOOH

COOHHC

O

48. In each compound, the most oxidized carbon will have the most positive oxidation number and,

commonly, the most bonds to oxygen. In contrast, the most reduced carbon will have the most negative

oxidation number and, commonly, the most bonds to hydrogen. The most reduced carbon has been

circled while an asterisk has been placed by the most oxidized carbon.

CHCH

CHO

HC

CH2OH

OHOH

OH

ribose(a sugar)

CCH3(CH2)16

O

OH

stearic acid(a fat)

CC

O

OH

O

CH3

pyruvic acid(a metabolite)

oxidation number = –1,two bonds to hydrogen

oxidation number = –3,three bonds to hydrogen

oxidation number = –3,three bonds to hydrogen

oxidation number = +1,two bonds to oxygen

oxidation number = +3,three bonds to oxygen

oxidation number = +3,three bonds to oxygen

*

**

49. (a)

(b)

(c) 2 CH3CH2OHþ 2 NaðmetalÞ ����! 2 CH3CH2ONaþ H2

(d)

(e)

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(f)

50.

51. A simple chemical test to distinguish between:

(a) ethanol and dimethyl ether. Ethanol will react readily with potassium dichromate and sulfuric acid

to make acetaldehyde. Visibly, the orange color of the dichromate changes to green. Ethanol reacts

with metallic sodium to produce hydrogen gas. Dimethyl ether does not react with either of these

reagents.

(b) 1-pentanol and 1-pentene. 1-pentene will rapidly decolorize bromine as it adds to the double bond.

1-pentanol does not react.

(c) p-methylphenol has acidic properties so it will react with sodium hydroxide. Methoxybenzene

does not have acidic properties and will not react with sodium hydroxide.

52. Isomers of C8H10O

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53. Only compound (a) will react with NaOH.

54. Order of increasing boiling points.1-pentanol < 1-octanol < 1,2-pentanediol

138�C 194�C 210�CAll three compounds are alcohols. 1-pentanol has the lowest molar mass and hence the lowest boiling

point. 1-octanol has a higher molar mass and therefore a higher boiling point than 1-pentanol. 1,2-

pentanediol has two��OH groups and therefore forms more hydrogen bonds than the other two alcohols

which causes its higher boiling point.

55. (a) The primary carbocation that is formed first is unstable.

Thus, the primary carbocation shifts to a much more stable, tertiary carbocation

It is this intermediate that goes on to form the major product, 2-methyl-2-butene.

(b) Hydration will not form 2-methyl- 1-butanol because the double bond lies between the middle two

carbons in 2-methyl-2-butene. By Markovnikov’s rule, the —H will add to the double bonded

carbon that already has a hydrogen. Thus, 2-methyl-2-butanol will be the major product.

56.

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