Janovsky reaction

What is Janovsky reaction?

The Janovsky reaction involves the reaction of aldehydes and ketones that contain α-methylene groups with m-dinitrobenzenes in the presence of a strong base.

Janovsky reaction - general reaction scheme
Janovsky reaction

This Janovsky reaction results in the formation of an intense purple coloration, which can be used to detect the presence of carbonyl compounds.


Janovsky, J.V. and Erb, L. (1886), Zur Kenntniss der directen Brom- und Nitrosubstitutionsproducte der Azokörper. [On the knowledge of the direct bromine and nitro substitution products of azo bodies.] Ber. Dtsch. Chem. Ges., 19: 2155-2158. https://doi.org/10.1002/cber.188601902113