Chapter 17, Problem 17.42P

Interpretation Introduction

(a)

Interpretation:

A complete mechanism for the given reaction is to be drawn. The major product of the reaction is to be predicted.

Concept introduction:

${\text{LiAlH}}_{\text{4}}$_, i.e., lithium aluminum hydride is a strong reducing reagent, capable of reducing carbonyl as well as nitrile groups. The active electron-rich species in it is a hydride ion. It reduces a carbonyl group to the corresponding alcohol and a nitrile group to a primary amine, via an imine.

This reduction must be carried out in a solvent containing no acidic protons because the ${\text{LiAlH}}_{\text{4}}$ is highly reactive toward solvents containing acidic protons. Ethers are the most suitable solvents.

Interpretation Introduction

(b)

Interpretation:

A complete mechanism for the reaction is to be drawn. The major product of the reaction is to be predicted.

Concept Introduction:

${\text{LiAlH}}_{\text{4}}$_, i.e., lithium aluminum hydride is a strong reducing reagent, capable of reducing carbonyl, nitrile, and imine groups. The active electron-rich species in it is a hydride ion. It reduces an imine group to an amine.

This reduction must be carried out in a solvent containing no acidic protons because ${\text{LiAlH}}_{\text{4}}$ is highly reactive toward solvents with acidic protons. Ethers are the most suitable solvents.

Interpretation Introduction

(c)

Interpretation:

A complete mechanism for the given reaction is to be drawn. The major product of the reaction is to be predicted.

Concept introduction:

${\text{NaBH}}_4$_, sodium borohydride is a reducing reagent, capable of reducing carbonyl as well as imine groups. The active electron-rich species in it is a hydride ion. It reduces an imine group to an amine.

Unlike ${\text{LiAlH}}_{\text{4}}$, ${\text{NaBH}}_4$ can tolerate weakly acidic solvents, so an alcohol or even water can be used as the solvent.