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CHAPTER 24
CARBOXYLIC ACIDS AND ESTERS
SOLUTIONS TO REVIEW QUESTIONS
1. (a) CH3COOH
(b)
(c)
(d)
(e)
(f)
(g) CH2
CHCOOH
(h)
(i) CH3CN
CH3COONa
(k)
(l)
(j)
O
(m) CH3(CH2)16COONa
(n) HO
P
O
OH
OH
(o) HO
P
OCH 3
OH
2. The butyric acid solution would be expected to have the more objectionable odor because salts normally
exhibit little or no odor. Salts are ionic and therefore have low volatility. For example, dilute solutions of
acetic acid (vinegar) have considerable odor, but sodium acetate does not.
3. Which has the greater solubility in water?
(a) Propanoic acid is more soluble than methyl propanoate.
(b) Sodium palmitate is more soluble than palmitic acid.
(c) Sodium stearate is more soluble than barium stearate.
(d) Sodium phenoxide is more soluble than phenol.
4. Unlike alkanes, carboxylic acids hydrogen bond tightly to each other. Thus, they have much higher
boiling points than alkanes.
5. (a) The major difference between fats and oils is that fats are solids at room temperature, oils
are liquids. The fatty acids in the molecules are mostly saturated in fats; more unsaturated
in oils.
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- Chapter 24 (b) Soaps are the sodium salts of high molar mass fatty acids. Syndets are synthetic detergents and
occur in several different forms. They have cleansing action similar to soaps, but have different
structural and solubility characteristics, such as being soluble in hard water. Some syndets also
contain long hydrocarbon chains.
(c) Hydrolysis is the breaking apart of an ester in the presence of water to form an alcohol and a
carboxylic acid. Mineral acids or digestive enzymes are used to speed the hydrolysis process.
Saponification breaks the ester apart using sodium hydroxide to form an alcohol and a salt of a
carboxylic acid.
6. A sour taste is associated with acids. Citrus fruits and rhubarb are examples of foods that have a sour,
acid taste.
7. Like a soap, a detergent contains a grease-soluble component and a water-soluble component.
The grease-soluble component of many molecules dissolves in the grease film. The watersoluble components attract water, causing small droplets of grease-bearing dirt to break loose and
float away.
8. The principal advantage of synthetic detergents over soap is that the syndets do not form insoluble
precipitates with the ions in hard water (Ca2þ, Mg2þ, Fe3þ).
9. Aspirin acts in the body as an antipyretic, an analgesic, and as an antiinflammatory agent.
10. In a condensation reaction one of the products formed is a small molecule such as water. In
polyester formation between an alcohol and a carboxylic acid, water is formed in addition to the
ester (polyester).
11. Polyesters are polymers of molecules linked together by ester bonds. The ester bonds are susceptible to
hydrolysis (being broken by reaction with water). When a polyester suture dissolves, the polymer’s
ester bonds are broken.
12. (a) Phosphoric acid anhydrides are used by living cells to store metabolic energy. The “energy
currency” of the cell is adenosine triphosphate (ATP) that contains two phosphoric acid
anhydrides.
(b) The phosphoric acid ester (or phosphate ester) has many important biochemical functions. Often a
phosphate ester is used to “tag” a biochemical, labeling it for specific biological uses.
13. Partial hydrogenation of oils is no longer commonly used by the food industry because this process
produces some trans fats. These fats are known to increase the risk of atherosclerosis.
14. MSG stands for monosodium glutamate. It is the sodium salt of the common amino acid, glutamic acid.
The sodium salt is formed in an acid-base reaction between glutamate and a base such as sodium
hydroxide.
15. Both compounds have a hydrophilic structural component. Capric acid contains a nine-carbon
hydrocarbon chain which decreases its solubility in water. Formic acid does not have a hydrocarbon
chain.
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- Chapter 24 16. An ester is formed by bonding an hydroxyl group (alcohol) to an acid with the release of water. This
compound meets the definition of ester because it combines phosphoric acid with ethanol.
O
HO
P
OCH 2 CH 3
OH
from
ethanol
from
phosphoric
acid
17. Hard water contains much higher concentrations of Ca2þ, Mg2þ, and Fe3þ ions than soft water. Soaps
precipitate (forming a soap scum) with these ions while synthetic detergents do not.
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SOLUTIONS TO EXERCISES
1. (a) lactic acid
(b) succinic acid
(c) phthalic acid (o-phthalic acid)
(d) propionic acid
2. (a) m-toluic acid
(b) b-chloropropionic acid
(c) butyric acid
(d) glutaric acid
3. (a) 2,3-dichloropropanoic acid
(b) hexanoic acid
(c) 2-methylbutanoic acid
(d) propanedioic acid
4. (a) propanoic acid
(b) 2,4-dimethylpentanoic acid
(c) butanedioic acid
(d) 2-hydroxybutanoic acid
OH
5. (a) CH3 CHCH2 COOH
(b) CH3CH2CH2CH2COOH
(c) CH3CH2COO Kþ
COOH
(d)
þ
(e) CH3 COO N a
CH3
(f) CH3CH2 CH2CCH 2COOH
CH3
CH3
(g)
COO H
6. (a) HOOCCH2COOH
OH
CH 2 CH 3
(b) CH3CH2CHCH2CHCOOH
Cl
(c) CH 3CHCOOH
(d)
- +
COO Na
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(e) HOOC
(f) CH3CH2COOH
COOH
þ
(g) CH3CH2CH2COOL i
7. (a) Acetic acid is a common name. The IUPAC name is ethanoic acid.
(b) 2-Bromo-1-hexanoic acid is incorrect because the carboxyl functional group should not be
numbered. The correct IUPAC name is 2-bromohexanoic acid.
(c) In a-chloropropanoic acid, the Greek letter is common nomenclature. The correct IUPAC name is
2-chloropropanoic acid.
8. (a) In b-bromobutanoic acid, the Greek letter is common nomenclature. The correct IUPAC name is
3-bromobutanoic acid.
(b) Lactic acid is a common name. The IUPAC name is 2-hydroxypropanoic acid.
(c) 3-Ethyl-5-pentanoic acid incorrectly includes a number for the carboxyl functional group. The
correct IUPAC name is 3-ethylpentanoic acid.
9. Increasing pH means increasing basicity
OH
< NaCl < NH3 < NaOH
HCl < CH3COOH <
Increasing pH
10. Decreasing pH means increasing acidity
OH
KOH > NH3 > KBr >
> HCOOH > HBr
Decreasing pH
11. (a) succinic acid
(b) butanoic acid
(c) acetic acid
(d) butanoic acid
12. (a) ethanoic acid
(b) propanoic acid
(c) ethanoic acid
(d) malonic acid
13. IUPAC and common names
(a) methyl propenoate
(b) ethyl butanoate
(c) phenyl-2-hydroxybenzoate
methyl acrylate
ethyl butyrate
phenyl salicylate
14. IUPAC and common names
(a) methyl methanoate
(b) propyl benzoate
(c) ethyl propanoate
methyl formate
propyl benzoate
ethyl propionate
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- Chapter 24 15. Structural formulas
(a)
(c)
(b)
16. Structural formulas
(a)
(c)
(b)
17. (a) Compounds are different: methyl propanoate and ethyl ethanoate
(b) Compounds are the same
(c) Compounds are different: methyl 2-methylpropanoate and isopropyl ethanoate
18. (a) Compounds are different: methyl benzoate and phenyl acetate
(b) Compounds are different: methyl acetate and methyl propanoate
(c) Compounds are the same
19. Structural formula for the ester that when hydrolyzed would yield:
(a)
(b)
(c)
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- Chapter 24 20. Structural formula for the ester that when hydrolyzed would yield:
(a)
(b)
(c)
21. Structural formulas for the reactants that will yield the following esters:
(a)
(b)
(c)
22. Structural formulas for the reactants that will yield the following esters:
(a)
(b)
(c)
23. (a) These reagents (Na2Cr2O7, H2SO4) oxidize the aldehyde to a carboxylic acid.
CH3
H3C
C
CH2
COOH
CH3
3,3-dimethylbutanoic acid
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- Chapter 24 (b) These reagents (Na2MnO4, NaOH, D) oxidize the alkyl side chain to form the salt of benzoic acid.
O
CO
Na
sodium benzoate
(c) This is an acid-base reaction that forms the salt of the carboxylic acid.
CH3CH2CH2COO Kþ
potassium butanoate
24. (a) These reagents (Na2MnO4, NaOH, D) oxidize the alkyl side chain to form the salt of benzoic acid.
O
CO
Na
sodium benzoate
(b) These reagents (Na2Cr2O7, H2SO4) oxidize the primary alcohol to a carboxylic acid.
CH3CH2CH2COOH
butanoic acid
(c) This is an acid-base reaction that forms the salt of the carboxylic acid.
CH3CH2COO Naþ
sodium propanoate
25. (a) A carboxylic acid reacts with a carboxylic acid chloride to yield a carboxylic acid anhydride.
O
CH3CH2CH 2
C
O
O
C
C H3
(b) A nitrile reacts with water to form a carboxylic acid.
CH3COOH
(c) A carboxylic acid chloride reacts with an alcohol to form an ester.
O
CH3CH2
C
OCH2CH3
26. (a) A nitrile reacts with water to form a carboxylic acid.
CH3CH2COOH
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- Chapter 24 (b) A carboxylic acid chloride reacts with an alcohol to form an ester.
O
CH3
OCH2CH2CH3
C
(c) A carboxylic acid reacts with an alcohol to form an ester.
O
H
C
OCH2 CH3
27. Simple test to distinguish between:
(a) Sodium benzoate and benzoic acid: Sodium benzoate is water soluble; benzoic acid is not.
(b) Maleic acid and malonic acid. Maleic acid has a carbon-carbon double bond, it will readily add
and decolorize bromine; malonic acid will not decolorize bromine.
28. Simple tests to distinguish between:
(a) Benzoic acid and ethyl benzoate; benzoic acid is an odorless solid; ethyl benzoate is a fragrant
liquid.
(b) Succinic acid and fumaric acid: fumaric acid has a carbon-carbon double bond and will readily add
and decolorize bromine; succinic acid will not decolorize bromine.
CH3 CH2 COO Naþ + H2 O
29. (a) CH3 CH2 COOH + NaOH
O
(b) CH3CH2COOH + CH3OH 99:
CH 3
CH3CH2COCH3 + H2O
CH 3
30. (a) CH3CHCH2COOH +
O
SOCl2 99: CH3CHCH2CCl + SO2 + HCl
CH3
CH3
O
(b) CH3CHCH2COOH + CH3CH2CH2OH 99: CH3CHCH2COCH2CH2CH3 + H2O
31. (a) These reagents (NaOH, H2O, D) cause saponification of the ester.
þ
CH3 OH þ CH3 CH2 COO Na
(b) These reagents (Hþ, H2O) cause hydrolysis of the ester.
CH3 CH2 OH þ CH3 COOH
32. (a) These reagents (Hþ, H2O) cause hydrolysis of the ester.
OH
CH3CHCH3
+ CH3C H2 C OOH
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- Chapter 24 (b) These reagents (NaOH, H2O, D) cause saponification of the ester.
þ
CH3 OH þ CH3 CH2 CH2 CH2 CH2 COO Na
O
O
33. (a) CH3CH2CH2COCH3 + H2O
HCl
O
(b)
CH3CH2CH2COH + CH3OH
O
HCOCH2CH3 + NaOH
99:
Δ
H2O
HCO– Na+ + CH3CH2OH
O
O
34. (a) CH3CH2COCH2CH3 + KOH
H2O
Δ
CH3CH2CO– K+ + CH3CH2OH
O
O
(b) CH3CH2CH2COCH2CH2CH3 + H2O
HCl
CH3CH2CH2COH + CH3CH2CH2OH
35. (a) These reagents (H2O, Hþ) cause hydrolysis of the diacylglycerol.
CH2 OH
CHOH
+ 2 CH3 (CH2 )10 COOH
CH2 OH
(b) These reagents (H2, Ni) reduce the double bond.
CH3 ðCH2 Þ14 COOH
(c) These reagents (H2, copper chromite, D, pressure) cause hydrogenolysis of the triacylglycerol.
CH2 OH
CHOH
+ 3 CH3 (CH2 )12 CH2 OH
CH2 OH
36. (a) These reagents (H2, Ni) reduce the double bond.
CH3 ðCH2 Þ16 COOH
(b) These reagents (H2, copper chromite, D, pressure) cause hydrogenolysis of the triacylglycerol.
CH2 OH
CHOH
+ 3 CH3 (CH2 )10 CH2OH
CH2 OH
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- Chapter 24 (c) These reagents (H2O, Hþ) cause hydrolysis of the triacylglycerol.
CH2 OH
+ 3 CH3 (CH2 )14 COO H
CHOH
CH2 OH
O
37. H2 C
O
C(CH 2 )12 CH 3
O
HC
O
C(CH 2 )12 CH 3
O
H2 C
O
C(CH 2 )12 CH 3
H2 C
OH
O
+ 3 H2O
H+
HC
OH
H2 C
OH
+ 3 CH3(CH2)12COH
O
38. H2 C
O
C(CH 2 )14 CH 3
O
HC
O
C(CH 2 )14 CH 3 + 6 H2
O
H2 C
O
C(CH 2 )14 CH 3
H2 C
copper chromite
Δ, pressure
HC
H2 C
OH
OH + 3 CH3(CH2)14CH2OH
OH
39. CH3(CH2)12COONa would be more useful than CH3(CH2)12COOH as a cleansing agent in soft water.
Both have a long hydrocarbon chain which would dissolve in the fat, but the acid is not water soluble,
whereas the sodium salt is soluble in water.
40. Sodium lauryl sulfate would be more effective as a detergent in hard water than sodium propyl sulfate
because the hydrocarbon chain is only three carbons long in the latter, not long enough to dissolve
grease well. Sodium lauryl sulfate is effective in both hard and soft water.
41. Only (a), hexadecyltrimethyl ammonium chloride would be a good detergent in water. It is cationic.
42. Only (c) CH3(CH2)10CH2O(CH2CH2O)7CH2CH2OH, would be a good detergent in water. It is
nonionic.
O
O
‘
‘
H+
43. (a) HO ¬ P ¬ OH + HOCH 2CH 3 99: HO ¬ P ¬ OCH 2CH 3 + H 2O
ƒ
ƒ
OH
OH
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- Chapter 24 -
O
O
‘
‘
+
H
(b) HO ¬ P ¬ OCH 2CH 3 + CH 3CH 2CH 2OH 99: HO ¬ P ¬ OCH 2CH 3 + H 2O
ƒ
ƒ
OH
OCH 2CH 2CH 3
O
O
‘
‘
H+
44. (a) HO ¬ P ¬ OH + 3 CH 3OH 99: CH 3O ¬ P ¬ OCH 3 + 3 H 2O
ƒ
ƒ
OCH 3
OH
O
O
‘
‘
H+
(b) HO ¬ P ¬ OH + CH 3OH 99:
CH 3O ¬ P ¬ OH + H 2O
ƒ
ƒ
OH
OH
O
O
CH 3
‘
‘
ƒ
H+
CH 3O ¬ P ¬ OH + CH 3CH 2CHCH 3 99: CH 3O ¬ P ¬ OCHCH 2CH 3
ƒ
ƒ
ƒ
OH
OH
OH
45. Grams and moles of sodium benzoate (NaC7H5O2):
0:001 1 lb 454 g
¼ 0:5 g sodium benzoate
1 lb
0:5 g NaC7 H5 O2 COOH
OH
46.
salicylic
acid
1 mol
¼ 3 103 mol NaC7 H5 O2
145:1 g
O
O
‘
‘
± CH3C ¬ O ¬ CCH3 ¡
acetic
anhydride
47. The ester is propyl propanoate
COOH
OCCH3
‘
± CH3COOH
O
aspirin
(acetylsalicylic acid)
acetic acid
CH 3CH 2COCH 2CH 2CH 3
‘
O
Compound A is an acid; B is an alcohol. If B is oxidized to an acid which is the same as A, then A and B
both have the same carbon structure, three carbon atoms each. The acid A must be propanoic acid,
CH3CH2COOH. The alcohol can be 1-propanol or 2-propanol. Only 1-propanol can be oxidized to
propanoic acid which is the same as compound A.
48. Phosgene (COCl2) contains two acid chloride functional groups. When phosgene (acid chlorides) reacts
with bisphenol A (alcohols), esters are formed.
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- Chapter 24 49. Polyesters are polymers of molecules linked together by ester bonds. The ester bonds are susceptible to
hydrolysis (being broken by reaction with water). When a polyester suture dissolves, the polymer’s
ester bonds are broken.
50. CH COOH Ð
3
þ
CH3 COO þ H
98:7%
1:3%
Of the total concentration of 0.1M, (0.013)(0.1M) is in the form of acetate. The acetate concentration is
0.0013M.
51. (a) There are two phosphoric acid esters and no phosphoric acid anhydrides.
(b) There is one phosphoric acid ester and one phosphoric acid anhydride.
52. Complete hydrogenation will convert the carbon-carbon double bonds to single bonds.
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53.
There are two other triacylglycerols containing all three of these acids. Each of the three acids can be
attached to the middle carbon of the glycerol.
54. Names and formulas of products are
(a)
(b)
(c)
O
‘
(d) CH 2 ¬ O ¬ C(CH 2)10CH 3
ƒƒ
ƒ
O
‘
CH ¬ O ¬ C(CH 2)14CH 3
ƒƒ
ƒ
O
‘
CH 2 ¬ O ¬ C(CH 2)16CH 3
lauroylpalmitoylsteroylglycerol
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55.
CH3
COOH
COOCH3
A
B
C
56.
57. C10H 12O2 ¡ C7H8O +
A (has a
B (alcohol)
benzene ring)
C3H6O2
C (acid)
O
CH3CH2C
OCH2
CH2OH
CH 3CH 2COOH
A
B
C
(1) C cannot be a benzene ring. If C is an acid, it must be propanoic acid. (2) If B is an alcohol and has a
benzene ring, it must be benzyl alcohol. Putting B and C together gives the ester A.
58. Smell both samples. Butanoic acid has an unpleasant rancid odor; ethyl butanoate has a pleasant odor of
pineapple.
59. Each molecule of triolein requires three molecules of H2 (one for each double bond)
3 22:4 L 3 mol H2
1 mol triolein
(a) ð1:00 kg trioleinÞ 10kg g 885:4
g triolein 1 mol triolein 1 mol H2 ¼ 75:9 L H2
g tristearin
(b) ð1:00 kg trioleinÞ 891:5
¼ 1:01 kg tristearin
885:4 g triolein
60. The statement is false. When methyl propanoate is hydrolyzed, propanoic acid and methanol are formed.
61. Esters of formula C5H10O2
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- Chapter 24 62. (a) Mass percent of oxygen in dacron.
Mass of one unit of dacron ¼ 192.2 g
Mass of oxygen in one unit of dacron ¼ 64.00 g
64:00 g O
100 ¼ 33:30% O
192:2 g
(b) Molar mass of 105 units
192:2 g
ð105 unitsÞ
¼ 2:02 104 g
unit
63. An alkyd polyester would most likely be thermosetting because glycerol is trifunctional and would thus
allow cross linking between chains in forming the ester polymer.
64. Synthesis of:
(a) acetic acid
K2 Cr2 O7
CH3 CH2 OH ! CH3 COOH
H2 SO4
(b) ethyl acetate
(c) b-hydroxybutyric acid
65. (a)
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(b)
OH
66.
HBr
H2SO4
Br
CN
KCN
COOH
H2O
H+
67. This polymer is formed as acids react with alcohols. Each reaction forms an ester splitting out a water
molecule in the process. Thus, this is a condensation reaction.
O
CH 2 C
O
O
O
CH C
O CH 2 C
CH 3
O
O
CH C
CH 3
O
n
This polymer has been formed with alternating glycolic acid and lactic acid monomers. Other arrangements
are possible.
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