Benzidine

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Benzidine
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. ^[1]

In common with benzidine some other aromatic amines such as 2-aminonaphthalene have been withdrawn from use in almost all industries because they are so carcinogenic.

In the past a common test for blood used benzidine but this has largely been replaced by tests using phenolphthalein / hydrogen peroxide and luminol.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.

[edit] 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].

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