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IUPAC name (2,4-dinitrophenyl)hydrazine
Other names 2,4-DNPH; 2,4-DNP; Brady's reagent
CAS number 119-26-6
SMILES NNc1ccc(cc1[N+]([O-])=O)[N+]([O-])=O
Molecular formula C6H6N4O4
Molar mass 198.14
Appearance Red or orange powder
Melting point

198 - 202 °C dec.

Solubility in water Slight
Main hazards Flammable, possible carcinogen
Except where noted otherwise, data are given for
materials in their standard state
(at 25 °C, 100 kPa)

Infobox disclaimer and references

2,4-Dinitrophenylhydrazine (or Brady's reagent) is the chemical compound C6H3(NO2)2NHNH2. Dinitrophenylhydrazine is relatively sensitive to shock and friction; it is a shock explosive so care must be taken with its use. It is a red to orange solid, usually supplied wet to reduce its explosive hazard. It is a substituted hydrazine, and is often used to qualitatively test for carbonyl groups. The hydrazone derivatives can also be used as evidence toward the identity of the original compound.



2,4-Dinitrophenylhydrazine is commercially available usually as a wet powder. It can be prepared by the reaction of hydrazine with 2,4-dinitrochlorobenzene.[1]

Brady's test

2,4-Dinitrophenylhydrazine can be used to qualitatively detect the carbonyl functionality of a ketone or aldehyde functional group. A positive test is signaled by a yellow or red precipitate (known as a dinitrophenylhydrazone):

RR'C=O + C6H3(NO2)2NHNH2 → C6H3(NO2)2NHNCRR' + H2O

This reaction can be described as a condensation reaction, with two molecules joining together with loss of water. It is also called addition-elimination reaction: nucleophilic addition of the -NH2 group to the C=O carbonyl group, followed by the removal of a H2O molecule.

The mechanism for the reaction between 2,4-dinitrophenylhydrazine and an aldehyde or ketone is shown:[2]

Crystals of different hydrazones have characteristic melting and boiling points, hence 2,4-dinitrophenylhydrazine can be used to distinguish between various compounds containing carbonyl groups. The method was particularly important because melting point determinations require only low-cost instrumentation. This application in analytical chemistry was developed by Brady and Elsmie.[3]


Dinitrophenylhydrazine does not react with other carbonyl-containing functional groups such as carboxylic acids, amides, and esters. For carboxylic acids, amides and esters, there is resonance associated stability as a lone-pair of electrons interacts with the p-orbital of the carbonyl carbon resulting in increased delocalisation in the molecule. This stability would be lost by addition of a reagent to the carbonyl group. Hence, these compounds are more resistant to addition reactions.

See also


  1. ^ Allen, C. F. H. (1943). "2,4-Dinitrophenylhydrazine". Org. Synth.; Coll. Vol. 2: 228. 
  2. ^ Adapted from Chemistry in Context, 4th Edition, 2000, Graham Hill and John Holman
  3. ^ Brady, O. L.; Elsmie, G. V. (1926). "The use of 2:4-dinitrophenylhydrazine as a reagent for aldehydes and ketones". Analyst 51: 77-78. doi:10.1039/AN9265100077.
This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "2,4-Dinitrophenylhydrazine". A list of authors is available in Wikipedia.
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