Imines and Imine Derivatives

IMINES AND IMINE DERIVATIVES

Nitrogen analogs of both aldehydes and ketones which have the same oxidation level are imines and imine derivatives. In almost every instance these compounds are prepared by an exchange reaction between an amine derivative and a car-bonyl compound. For simple imines (R = alkyl, aryl) water removal by either a dehydrating agent (KOH or molecular sieves) or azeotropic distillation is often employed to drive the reaction to completion.

A wide variety of other R groups attached to nitrogen can be used and all give the C=N bond formation with loss of water. However, most of these substitutions on the nitrogen atom reduce the nucleophilicity of the amino group so acid catalysis is used to facilitate the reaction. Many of these nitrogen derivatives of aldehydes and ketones have very interesting chemistry in their own right. These derivatives also serve as a classic way to identify aldehydes and ketones. Many of these derivatives tend to be solids with characteristic melting points. Thus conversion of an aldehyde or ketone to a derivative, such as oxime or a 2,4-dinitrophenylhydrazone (2,4-DNPH) derivative, produces a solid with a distinct melting point. Comparison of the melting point with the known value can be used to confirm the structure of the aldehyde or ketone.