Chapter 9, Problem 9.18P

(a)

Interpretation Introduction

Interpretation:

The alkyl halide has to be selected from the given set of alkyl halides, which shows the greater rate of ${\text{S}}_{\text{N}}2$ reaction with ${\text{KN}}_{\text{3}}$ in acetone.

Concept Introduction:

• ${\text{S}}_{\text{N}}2$ reaction: It is a nucleophilic substitution reaction in which the rate determining step depends on both alkyl halide and the nucleophile present. The bond making and the bond breaking process happens simultaneously in this reaction, which results in the inversion of configuration.
• $\text{Rate}\text{= k}\left[\text{alkylhalide}\right]\text{×}\left[\text{nucleophile}\right]$
• Structure of the substrate plays a major role in ${\text{S}}_{\text{N}}2$ reaction. If the substrate is more substituted the rate of the reaction becomes slower. Since the mechanism of ${\text{S}}_{\text{N}}2$ reaction proceeds through backside attack on the substrate it depends on steric factor of reactant and nucleophile.
• Polar aprotic solvent is good for ${\text{S}}_{\text{N}}2$ reaction because it is not interact with nucleophile.
• Less basic good or moderate nucleophile is good for ${\text{S}}_{\text{N}}2$ reaction because it is not abstract a proton only attacks the positive center only.
• Better leaving group is good for ${\text{S}}_{\text{N}}2$ reaction because removal of leaving group also be in rate determining step in ${\text{S}}_{\text{N}}2$ reaction.

(b)

Interpretation Introduction

Interpretation:

The alkyl halide has to be selected from the given set of alkyl halides, which shows the greater rate of ${\text{S}}_{\text{N}}2$ reaction with ${\text{KN}}_{\text{3}}$ in acetone.

Concept Introduction:

• ${\text{S}}_{\text{N}}2$ reaction: It is a nucleophilic substitution reaction in which the rate determining step depends on both alkyl halide and the nucleophile present. The bond making and the bond breaking process happens simultaneously in this reaction, which results in the inversion of configuration.
• $\text{Rate}\text{= k}\left[\text{alkylhalide}\right]\text{×}\left[\text{nucleophile}\right]$
• Structure of the substrate plays a major role in ${\text{S}}_{\text{N}}2$ reaction. If the substrate is more substituted the rate of the reaction becomes slower. Since the mechanism of ${\text{S}}_{\text{N}}2$ reaction proceeds through backside attack on the substrate it depends on steric factor of reactant and nucleophile.
• Polar aprotic solvent is good for ${\text{S}}_{\text{N}}2$ reaction because it is not interact with nucleophile.
• Less basic good or moderate nucleophile is good for ${\text{S}}_{\text{N}}2$ reaction because it is not abstract a proton only attacks the positive center only.
• Better leaving group is good for ${\text{S}}_{\text{N}}2$ reaction because removal of leaving group also be in rate determining step in ${\text{S}}_{\text{N}}2$ reaction.