It07:2,4-DNPH

This article is about the compound 2,4-dinitrophenylhydrazine, otherwise known as 2,4-DNPH or Brady's Reagent. It is a substituted hydrazine (H2N=NH2) and is most commonly used as a qualitative test for the presence of the carbonyl functional group (C=O).

Synthesis

2,4-DNPH can be synthesized via the electrophilic substitution reaction of hydrazine with 2,4-Dinitrochlorobenzene. This synthesis was carried out by . The reaction scheme and mechanism of this reaction is shown below.

Reaction with Carbonyl Compounds

The products obtained from this reaction are water and a hydrazone. A hydrazone is a class of organic compound which contains the C=N double bond, with the general formula of R2C=NR2. As water is eliminated in the Brady's Reaction, we can see that this reaction is a simple condensation process.

The 2,4-DNPH derivatives obtained from the reaction of 2,4-DNPH with the various carbonyl compounds have distinct characteristic colours and boiling points. As such, it is possible to identify the carbonyl compound given the hydrazone product. Some examples of aldehydes and ketones and the boiling points of their respective hydrazones are given below.