A
Schiff base, named after
Hugo Schiff, is a compound with the general structure R
2C=NR' (R' ≠ H). They can be considered a sub-class of
imines, being either secondary ketimines or secondary aldimines depending on their structure. The term is often synonymous with
azomethine which refers specifically to secondary
aldimines (i.e. R-CH=NR' where R' ≠ H).