Chapter 9, Problem 9.12P

Interpretation Introduction

(a)

Interpretation:

The reaction, either ${\text{S}}_{\text{N}}{\text{1, S}}_{\text{N}}\text{2}$, or $\text{E1, E2}$ is favored at a high concentration of ${\text{HS}}^{\text{-}}$ is to be explained.

Concept introduction:

${\text{S}}_{\text{N}}\text{2}$ reaction rates are highly sensitive to nucleophilicity whereas ${\text{S}}_{\text{N}}\text{1}$ reactions are not. Thus, strong nucleophiles favor ${\text{S}}_{\text{N}}\text{2}$ reactions and weak nucleophiles favor ${\text{S}}_{\text{N}}\text{1}$ reactions.

$\text{E2}$ reaction rates are highly sensitive to the strength of the attacking base whereas $\text{E1}$ reactions are not. Thus, strong bases favor $\text{E2}$ reactions, and weak bases favor $\text{E1}$ reactions.

Interpretation Introduction

(b)

Interpretation:

The reaction, either ${\text{S}}_{\text{N}}{\text{1, S}}_{\text{N}}\text{2}$, or $\text{E1, E2}$ favored at low concentration of ${\text{HS}}^{\text{-}}$ is to be explained.

Concept introduction:

${\text{S}}_{\text{N}}\text{2}$ reaction rates are highly sensitive to nucleophilicity whereas ${\text{S}}_{\text{N}}\text{1}$ reactions are not. Thus, strong nucleophiles favor ${\text{S}}_{\text{N}}\text{2}$ reactions and weak nucleophiles favor ${\text{S}}_{\text{N}}\text{1}$ reactions.

$\text{E2}$ reaction rates are highly sensitive to the strength of the attacking base whereas $\text{E1}$ reactions are not. Thus, strong bases favor $\text{E2}$ reactions and weak bases favor $\text{E1}$ reactions.