Chapter 23.SE, Problem 45MP

Interpretation Introduction

Interpretation:

A mechanism for the first step in the Mannich reaction shown, a reaction between acetaldehyde and dimethyl amine, to yield an iminium ion intermediate along with water is to be proposed. The structure of the iminium ion intermediate is to be given. Further the mechanism of the second step involving the reaction between iminium ion intermediate and cyclohexanone is also to be proposed.

Concept introduction:

The steps involved in the formation of the iminium ion are i) Protonation of the aldehyde ii) Nucleophilic attack of the amine on the protonated aldehyde iii) A proton exchange iv) Loss of water to yield the iminium ion.

The reaction between iminium ion intermediate and cyclohexanone takes place through the following steps i) Reaction between the enol form of the cyclohexanone and iminium ion ii) Deprotonation of the intermediate.

To propose:

A mechanism for the first step in the Mannich reaction shown, a reaction between acetaldehyde and dimethyl amine, to yield an iminium ion intermediate along with water. To show the structure of the iminium ion intermediate.

Further to propose a mechanism for the second step involving the reaction between iminium ion intermediate and cyclohexanone.