Chapter 7, Problem 55P

(a)

Interpretation Introduction

Interpretation: The rate constant for first order solvolysis reaction of $\left[\text{(1-Bromo-1-methyl)ethyl}\right]\text{benzene}$ should be calculated.

Concept introduction:Haloalkane solvolysis with ethanol, methanol or water is a typical example for unimolecuar substitution. It proceeds via two-step mechanism. The first slow step that determines rate is the removal of 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 unimolecuar substitution. The final step is attack of nucleophile on carbocation generated and formation of racemic products.

Tertiary or secondary halides undergo fastest unimolecuar substitution as they can readily form the tertiary carbocation followed by secondary and least reactive are primary.

(b)

Interpretation Introduction

Interpretation: The rate constant for first order solvolysis reaction of $\left[\text{(1-Bromo-1-methyl)ethyl}\right]\text{benzene}$ in presence of $0.1\text{ M LiCl}$ should be calculated and the reason behind increased rate should be suggested.

Concept introduction: Haloalkane solvolysis with ethanol, methanol or water is a typical example for unimolecuar substitution. It proceeds via two-step mechanism. The first slow step that determines rate is the removal of 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 unimolecuar substitution. The final step is attack of nucleophile on carbocation generated and formation of racemic products.

Tertiary or secondary halides undergo fastest unimolecuar substitution as they can readily form the tertiary carbocation followed by secondary and least reactive are primary.

(c)

Interpretation Introduction

Interpretation: The rate constant for first order solvolysis reaction of $\left[\text{(1-Bromo-1-methyl)ethyl}\right]\text{benzene}$ in presence of $0.1\text{ M LiBr}$ should be calculated and the reason behind decreased rate should be suggested.

Concept introduction: Haloalkane solvolysis with ethanol, methanol or water is a typical example for unimolecuar substitution. It proceeds via two-step mechanism. The first slow step that determines rate is the removal of 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 unimolecuar substitution. The final step is attack of nucleophile on carbocation generated and formation of racemic products.

Tertiary or secondary halides undergo fastest unimolecuar substitution as they can readily form the tertiary carbocation followed by secondary and least reactive are primary.