General structure of an imine. Schiff bases are imines in which R3 is an alkyl or aryl group (not a hydrogen). R1 and R2 may be hydrogensGeneral structure of an azomethine compound
In organic chemistry, a Schiff base (named after Hugo Schiff) is a compound with the general structure R1R2C=NR3 (R3 = alkyl or aryl, but not hydrogen).[1][2] They can be considered a sub-class of imines, being either secondary ketimines or secondary aldimines depending on their structure. Anil refers to a common subset of Schiff bases: imines derived from anilines.[3] The term can be synonymous with azomethine which refers specifically to secondary aldimines (i.e. R−CH=NR' where R' ≠ H).[4]