Chapter 8, Problem 8.38P

Interpretation Introduction

(a)

Interpretation:

The mechanism, ${\text{S}}_{\text{N}}{\text{1 or S}}_{\text{N}}\text{2}$, for the given mechanism is to be explained.

Concept introduction:

The unimolecular nucleophilic substitution reaction is the first order reaction, that is, the reaction rate is directly proportional to the concentration of substrate; independent of the concentration of the nucleophile or the base.

The bimolecular nucleophilic substitution ${\text{(S}}_{\text{N}}\text{2)}$ reaction is the second order reaction, that is, the reaction rate is directly proportional to both the concentration of substrate and the concentration of the nucleophile or the base.

Interpretation Introduction

(b)

Interpretation:

The complete mechanism with appropriate arrows for the given reaction is to be drawn.

Concept introduction:

A unimolecular nucleophilic substitution (${\text{S}}_{\text{N}}\text{1}$) reaction consists of two steps. First, the leaving group leaves in a heterolysis step, yielding a carbocation intermediate, then a nucleophile attacks the carbocation in a coordination step. Intermediates are not included in the overall mechanism.

Interpretation Introduction

(c)

Interpretation:

The change in the reaction rate, if the concentration of $\text{KI}$ is doubled, is to be explained.

Concept introduction:

The unimolecular nucleophilic substitution reaction is the first order reaction, that is, the reaction rate is directly proportional to the concentration of the substrate; independent of the concentration of the nucleophile or the base.