Chapter 8, Problem 8.68P

Interpretation Introduction

Interpretation:

The stereoisomer of $\text{α-bromo acid}$ that would be necessary to produce $\text{L-alanine}$, in which the R group is ${\text{CH}}_{\text{3}}$, is to be drawn assuming the reaction follows an ${\text{S}}_{\text{N}}\text{2}$ pathway

Concept introduction:

A ${\text{S}}_{\text{N}}\text{2}$  reaction is a single-step reaction. The incoming nucleophile attacks the carbon that is bonded to the leaving group, with the leaving group breaking off simultaneously with its bond pair. The incoming group must attack the carbon from the direction opposite to the leaving group. The result is generally a single product. As ${\text{S}}_{\text{N}}\text{2}$ reaction is a single-step reaction, the stereo specificity suggests that the nucleophile attacks the substrate exclusively from the side opposite to the leaving group producing a single stereoisomer. Thus,  ${\text{S}}_{\text{N}}\text{2}$ reactions are stereospecific.