Chapter 7, Problem 50P

(a)

Interpretation Introduction

Interpretation: The mistake in the mechanism of indicated reaction should be pointed out and correction should be proposed.

  

Concept introduction:Carbocation formation is relatively slower than acid-base reactions. Carbocations generated from alkyl halides have two fates; they can be either trapped by nucleophiles to give substitution product or may deprotonate to yield a small amount of alkene.

Unimolecular substitution or ${\text{S}}_{\text{N}}1$ proceeds via a two-step mechanism. The first slow step that determines the rate is the removal of the leaving group from the substrate haloalkane and generates a carbocation. Since the rate is only governed by substrate alone and no other nucleophile or solvent it is termed as a unimolecular substitution. The final step is the attack of the nucleophile on carbocation generated and the formation of racemic products.

A general ${\text{S}}_{\text{N}}1$ reaction mechanistic pathway is illustrated below:

  

(b)

Interpretation Introduction

Interpretation: The mistake in the mechanism of indicated reaction should be pointed out and correction should be proposed.

  

Concept introduction:Carbocation formation is relatively slower than acid-base reactions. Carbocations generated from alkyl halides have two fates; they can be either trapped by nucleophiles to give substitution product or may deprotonate to yield a small amount of alkene.

Unimolecular substitution or ${\text{S}}_{\text{N}}1$ proceeds via a two-step mechanism. The first slow step that determines the rate is the removal of the leaving group from the substrate haloalkane and generates a carbocation. Since the rate is only governed by substrate alone and no other nucleophile or solvent it is termed as a unimolecular substitution. The final step is the attack of the nucleophile on carbocation generated and the formation of racemic products.

A general ${\text{S}}_{\text{N}}1$ reaction mechanistic pathway is illustrated below:

  

(c)

Interpretation Introduction

Interpretation: The mistake in the mechanism of indicated reaction should be pointed out and correction should be proposed.

  

Concept introduction: Carbocation formation is relatively slower than acid-base reactions. Carbocations generated from alkyl halides have two fates; they can be either trapped by nucleophiles to give substitution product or may deprotonate to yield a small amount of alkene.

Unimolecular substitution or ${\text{S}}_{\text{N}}1$ proceeds via a two-step mechanism. The first slow step that determines the rate is the removal of the leaving group from the substrate haloalkane and generates a carbocation. Since the rate is only governed by substrate alone and no other nucleophile or solvent it is termed as anunimolecular substitution. The final step is the attack of the nucleophile on carbocation generated and the formation of racemic products.

A general ${\text{S}}_{\text{N}}1$ reaction mechanistic pathway is illustrated below: