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Benzidine is a synthetic chemical that does not occur naturally. It is a
crystalline (sandy or sugar-like) solid that may be grayish-yellow,
white, or reddish-gray in color.
Benzidine, the trivial name for 4,4'-diaminobiphenyl, is the solid
organic compound with the formula (C6H4NH2)2. This aromatic amine is a
component of a test for cyanide and also in the production of dyes.
Benzidine and its congeners constitute a family of similar synthetic
aromatic amines which are important precursors in the synthesis of dyes.
Some of these dyes have the potential to metabolize to aromatic amines
that are considered to be carcinogenic.
past, industry used large amounts of benzidine to produce dyes for
cloth, paper, and leather. However, it has not been manufactured for
sale in the United States since the mid-1970s.
Benzidine also has other names, such as 4,4'-diphenylenediamine or Fast
Corinth Base B (a registered trade name).
Benzidine and the substituted benzidines find vide applications as an
intermediate in the dyestuff industries and are largely used in the
synthesis of azo dyes.
Benzidine is prepared in a two step process from nitrobenzene. First,
the nitrobenzene is converted to 1,2-diphenylhydrazine, usually using
iron powder as the reducing agent. Treatment of this hydrazine with
mineral acids induces a rearrangement reaction to 4,4'-benzidine.
Smaller amounts of other isomers are also formed. The benzidine
rearrangement, which proceeds intramolecularly, is a classic mechanistic
puzzle in organic chemistry.
4,4-Diamino-1,1-biphenyl (benzidine) 1 is a well known compound, which
has been widely used in the past in different areas of science.
Molecules of this class were employed for a long time asprimary
materials in the manufacture of azodyes.
Benzidines also play an important role in cell biology and clinical work
as valuable staining reagents. Due to its potential risks, research has
been carried out to develop analogues for biological and medical
Benzidine - based dyes are largely classified as direct dyes, since they
may be applied directly to fabrics or other substrates without
pre-treatment or without subsequent processes that firmly attach the dye
to the substrate.
The majority of the dye works in
Hong Kong buy their dyes from Asian dye manufacturers, primarily from
China, Taiwan, India, Thailand and Southern Korea. The main reason is
the price differential between Western and Asian dyes where the latter
is approximately half - price.
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