Chapter 10, Problem 10.31P

Interpretation Introduction

(a)

Interpretation:

The alcohol that would be required to form the given alkyl chloride using ${\text{PCl}}_{\text{3}}$ is to be drawn.

Concept introduction:

For nucleophilic substitution and elimination reactions, ${\text{HO}}^{\text{-}}$ is a poor leaving group, whereas halides such as ${\text{Br}}^{\text{-}}$ and ${\text{Cl}}^{\text{-}}$ are quite good. To carry out a nucleophilic substitution or elimination reaction at a carbon atom that is attached to an OH group, first that alcohol is converted into an alkyl chloride or alkyl bromide. ${\text{PCl}}_{\text{3}}$ converts an alcohol into an alkyl chloride. This is a stereospecific reaction. It takes place with inversion of configuration at the alcohol carbon atom.

Interpretation Introduction

(b)

Interpretation:

The complete, detailed mechanism by which the transformation of the given compound would occur is to be drawn.

Concept introduction:

A much better way to convert an alcohol into an alkyl halide is to use ${\text{PCl}}_{\text{3}}$. The reaction is stereospecific. It takes place with inversion of configuration at the alcohol carbon atom. Two step mechanism occurs, which consists of back- to-back ${\text{S}}_{\text{N}}\text{2}$ steps.