C. Formation of Imines and Related Compounds

The reaction of aldehydes and ketones with ammonia or 1º-amines forms imine derivatives, also known as Schiff bases, (compounds having a C=N function). This reaction plays an important role in the synthesis of 2º-amines, as discussed earlier. Water is eliminated in the reaction, which is acid-catalyzed and reversible in the same sense as acetal formation.

D. Enamine Formation

The previous reactions have all involved reagents of the type: Y–NH₂, i.e. reactions with a 1º-amino group. Most aldehydes and ketones also react with 2º-amines to give products known as enamines.

Two examples of these reactions are presented in the following diagram. It should be noted that, like acetal formation, these are acid-catalyzed reversible reactions in which water is lost. Consequently, enamines are easily converted back to their carbonyl precursors by acid-catalyzed hydrolysis.