alcohols, ethers, phenols, and thiolsfaculty.chemeketa.edu/lemme/heinsolutions/ch22.pdf · c22...
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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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