Chapter 18, Problem 18.10P

Interpretation Introduction

Interpretation:

The complete and detailed mechanism for the formation of the imine from the aldehyde in Equation 18-18 is to be drawn.

Concept introduction:

Aldehydes react with ammonia and ${\text{1}}^{\text{o}}$ or ${\text{2}}^{\text{o}}$ amines to form imines under mildly acidic conditions. Ammonia and amines are moderately strong nucleophiles and can add reversibly to the carbonyl carbon. Activation of the carbonyl group is not necessary. The oxygen becomes negatively charged as a result of the nucleophilic addition. The negatively charged oxygen then extracts two protons from two other molecules of ammonia or amine and is converted to the good leaving group $-{\text{O}}^{\text{+}}{\text{H}}_{\text{2}}$. The heterolysis of this group forms a resonance stabilized carbocation. The cation extracts a proton from another molecule of ammonia or amine to form the final product as a mixture of isomers.