Chapter 20 - Organic Chemistry

Chapter 20

3-Methylbutanoic acid

4-Bromopentanoic acid

2-Ethylpentanoic acid

cis-4-Hexenoic acid

2,4-Dimethylpentanenitrile

cis-1,3-Cyclopentanedicarboxylic acid

The structure of 2,3-dimethylhexanoic acid. Methyl groups are attached to C 2 and C 3. C 1 is part of the C O O H group.

The structure of 4-methylpentanoic acid, a five-carbon chain with a methyl group attached to C 4. C 1 is part of the C O O H group.

The structure of trans-1,2-cyclobutanedicarboxylic acid. C O O H groups are attached to C 1 and C 2 of a cyclobutane ring, trans to one another.

The structure of o-hydroxybenzoic acid. A C O O H group is present on C 1 of benzene ring. The ortho position is connected to the O H group.

Dissolve the mixture in ether, extract with aqueous NaOH, separate and acidify the aqueous layer, and extract with ether.

43%

82% dissociation

73% dissociation

Lactic acid is stronger because of the inductive effect of the −OH group.

The dianion is destabilized by repulsion between charges.

More reactive

p-Methylbenzoic acid < Benzoic acid < p-Chlorobenzoic acid

Acetic acid < Benzoic acid < p-Nitrobenzoic acid

1. Mg; 2. CO₂; 3. H₃O⁺

1. Mg; 2. CO₂; 3. H₃O⁺ or 1. NaCN; 2. H₃O⁺

1. NaCN; 2. H₃O⁺; 3. LiAlH₄

1. PBr₃; 2. NaCN; 3. H₃O⁺; 4. LiAlH₄

Propanenitrile + CH₃CH₂MgBr, then H₃O⁺

p-Chlorobenzonitrile + CH₃MgBr, then H₃O⁺

1. NaCN; 2. CH₃CH₂MgBr, then H₃O⁺

A carboxylic acid has a very broad − OH absorption at 2500–3300 cm⁻¹.

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.