Chapter 8, Problem 8.66P

Interpretation Introduction

(a)

Interpretation:

The appropriate curved arrows for the given reaction are to be drawn.

Concept introduction:

In the ${\text{S}}_{\text{N}}\text{2}$ step, the substrate undergoes substitution in which one atom or group of atoms is replaced by another. A nucleophile attacks and forms a bond with the electrophilic carbon atom. A nucleophile forms a bond to the substrate; at the same time, a bond to the leaving group, i.e., the group that is displaced, is broken. In the ${\text{S}}_{\text{N}}\text{2}$ step, a curved arrow is drawn from the lone pair of the electron rich atom of the nucleophile to the electron poor atom of the substrate. A second curved arrow is drawn to indicate the breaking of the bond.

Interpretation Introduction

(b)

Interpretation:

The reason the reaction takes place with S as the nucleophilic atom instead of one of the negatively charged O atoms on $\text{methionine}$ is to be suggested.

Concept introduction:

The charge repulsion between the reacting species prevents any negatively charged atom from acting as a nucleophile.