Illustrated Glossary of Organic Chemistry

Hydrazone: A functional group containing the R2C=N-NR2 moiety, or a molecule containing this functional group.

General hydrazone structure.

Reaction of acetone with hydrazine gives propan-2-ylidenehydrazine, a simple hydrazone.

Reaction of benzaldehyde with 2,4-dinitrophenylhydrazine (2,4-DNPH) gives 1-benzylidene-2-(2,4-dinitrophenyl)hydrazine. Hydrazones derived from 2,4-DNPH are often colored (red or orange) due to extensive conjugation.