Chapter 21, Problem 21.48P

Interpretation Introduction

(a)

Interpretation:

The synthesis of the given compound from 3-methylpentanoic acid is to be shown.

Concept introduction:

Bromination of carboxylic acid occurs in the presence of some phosphorus trihalide or elemental phosphorus. This kind of bromination is called a Hell–Volhard–Zelinsky (HVZ) reaction. ${\text{PBr}}_3$ is produced [${\text{Br}}_{\text{2}}{\text{ + PCl}}_{\text{3}}{\text{, or Br}}_{\text{2}}\text{ + P}\left(\text{s}\right)$]. ${\text{PBr}}_3$ converts the carboxylic acid to an acid bromide. In the acid bromide form, the enol becomes more favorable, which facilitates the substitution reaction in the subsequent steps to produce the $\text{α}$-bromoacid bromide. Then treatment with water hydrolyzes the acid bromide to reform the carboxylic acid. The excellent ability of ${\text{Br}}^{\text{-}}$ as a leaving group makes $\text{α}$-bromoacids useful synthetic intermediates.

Interpretation Introduction

(b)

Interpretation:

The synthesis of the given compound from 3-methylpentanoic acid is to be shown.

Concept introduction:

Bromination of carboxylic acid occurs in the presence of some phosphorus trihalide or elemental phosphorus. This kind of bromination is called a Hell–Volhard–Zelinsky (HVZ) reaction. ${\text{PBr}}_3$ is produced [${\text{Br}}_{\text{2}}{\text{ + PCl}}_{\text{3}}{\text{, or Br}}_{\text{2}}\text{ + P}\left(\text{s}\right)$]. ${\text{PBr}}_3$ converts the carboxylic acid to an acid bromide. In the acid bromide form, the enol becomes more favorable, which facilitates the substitution reaction in the subsequent steps to produce the $\text{α}$-bromoacid bromide. Then treatment with water hydrolyzes the acid bromide to reform the carboxylic acid. The excellent ability of ${\text{Br}}^{\text{-}}$ as a leaving group makes $\text{α}$-bromoacids useful synthetic intermediates.

Interpretation Introduction

(c)

Interpretation:

The synthesis of the given compound from 3-methylpentanoic acid is to be shown.

Concept introduction:

Bromination of carboxylic acid occurs in the presence of some phosphorus trihalide or elemental phosphorus. This kind of bromination is called a Hell–Volhard–Zelinsky (HVZ) reaction. ${\text{PBr}}_3$ is produced [${\text{Br}}_{\text{2}}{\text{ + PCl}}_{\text{3}}{\text{, or Br}}_{\text{2}}\text{ + P}\left(\text{s}\right)$]. ${\text{PBr}}_3$ converts the carboxylic acid to an acid bromide. In the acid bromide form, the enol becomes more favorable, which facilitates the substitution reaction in the subsequent steps to produce the $\text{α}$-bromoacid bromide. Then treatment with water hydrolyzes the acid bromide to reform the carboxylic acid. The excellent ability of ${\text{Br}}^{\text{-}}$ as a leaving group makes $\text{α}$-bromoacids useful synthetic intermediates.