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Chapter 20

Problem 20-1
(a)
3-Methylbutanoic acid
(b)
4-Bromopentanoic acid
(c)
2-Ethylpentanoic acid
(d)
cis-4-Hexenoic acid
(e)
2,4-Dimethylpentanenitrile
(f)
cis-1,3-Cyclopentanedicarboxylic acid
Problem 20-3
Dissolve the mixture in ether, extract with aqueous NaOH, separate and acidify the aqueous layer, and extract with ether.
Problem 20-5
(a)
82% dissociation
(b)
73% dissociation
Problem 20-6
Lactic acid is stronger because of the inductive effect of the  −OH group.
Problem 20-7
The dianion is destabilized by repulsion between charges.
Problem 20-8
More reactive
Problem 20-9
(a)
p-Methylbenzoic acid < Benzoic acid < p-Chlorobenzoic acid
(b)
Acetic acid < Benzoic acid < p-Nitrobenzoic acid
Problem 20-10
(a)
1. Mg; 2. CO2; 3. H3O+
(b)
1. Mg; 2. CO2; 3. H3O+ or 1. NaCN; 2. H3O+
Problem 20-11
1. NaCN; 2. H3O+; 3. LiAlH4
Problem 20-12
1. PBr3; 2. NaCN; 3. H3O+; 4. LiAlH4
Problem 20-13
(a)
Propanenitrile + CH3CH2MgBr, then H3O+
(b)
p-Chlorobenzonitrile + CH3MgBr, then H3O+
Problem 20-14
1. NaCN; 2. CH3CH2MgBr, then H3O+
Problem 20-15
A carboxylic acid has a very broad  − OH absorption at 2500–3300 cm−1.
Problem 20-16
4-Hydroxycyclohexanone: H–C–O absorption near 4 δ in the 1H spectrum and C═O absorption near 210 δ in the 13C spectrum. Cyclopentanecarboxylic acid: –CO2H absorption near 12 δ in the 1H spectrum and  –CO2H absorption near 170 δ in the 13C spectrum.
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