Chapter 18, Problem 18.12P

Interpretation Introduction

Interpretation:

Whether imine formation shown can take place under basic conditions is to be determined.

Concept introduction:

The formation of an imine from a carbonyl compound involves a nucleophilic addition followed by a series of proton transfers. The final step is the elimination of the water molecule.

Ammonia and ${\text{1}}^{\text{o}}$ and ${\text{2}}^{\text{o}}$ amines are sufficiently nucleophilic to be able to attack a carbonyl carbon even without activation of the carbonyl group. The negatively charged oxygen that results from the addition of the amine is a strong base and can be protonated by water even under basic conditions. However, the final elimination step is not possible as the neutral $-\text{OH}$ group produced is a poor leaving group. The elimination of a hydroxyl group requires the conversion to the good leaving group ${-}^{+}{\text{OH}}_2$ via protonation. This is possible only under strongly acidic conditions.