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IUPAC name 4,4'-diaminobiphenyl
Other names Benzidine
Molecular formula C12H12N2
Molar mass 184.25
CAS number 92-87-5
Except where noted otherwise, data are given for
materials in their standard state
(at 25 °C, 100 kPa)
Infobox disclaimer and references

Benzidine is the trivial name for 4,4'-diaminobiphenyl, a carcinogenic aromatic amine which has been used as part of a test for cyanide and also in the synthesis of dyes. It has been linked to bladder cancer and pancreatic cancer.

Additional recommended knowledge

In common with benzidine some other aromatic amines such as 2-aminonaphthalene have been withdrawn from use in almost all industries because they are so carcinogenic.

In the past a common test for blood used benzidine but this has largely been replaced by tests using phenolphthalein / hydrogen peroxide and luminol. An enzyme in blood causes the benzidine to be oxidized to a polymer which is blue coloured. The test for cyanide uses similar chemistry to give the blue colour.

Benzidine is a known human carcinogen. [1]

Benzidine rearrangement

In a classic rearrangement reaction called the benzidine rearrangement benzidine is formed by reaction of the 1,2-diphenylhydrazine (PhNHNHPh) with acids. One plausible reaction mechanism has both hydrazine nitrogen atoms protonated after which a sigmatropic reaction takes place [2].


  1. ^ Link
  2. ^ Advanced Organic Chemistry third edition Jerry March ISBN 047185472-7
This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Benzidine". A list of authors is available in Wikipedia.
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