3,3'-Dichlorobenzidine is an

organic compound Some chemical authorities define an organic compound as a chemical compound that contains a carbon–hydrogen or carbon–carbon bond; others consider an organic compound to be any chemical compound that contains carbon. For example, carbon-co ...

with the formula (C₆H₃Cl(NH₂))₂. The pure compound is pale yellow, but commercial samples are often colored. It is barely soluble in water and is often supplied as a wet paste. It is widely used in the production of diarylide yellow pigments used in the production of printing inks. Its use in the production of dyes has been largely discontinued because of concerns about carcinogenicity.

Preparation and reactions

3,3'-Dichlorobenzidine is prepared in two steps from

2-nitrochlorobenzene 2-Nitrochlorobenzene is an organic compound with the formula ClC6H4NO2. It is one of three isomeric nitrochlorobenzenes. It is a yellow crystalline solid that is important as a precursor to other compounds due to its two functional groups. Sy ...

. The first step involves reduction with zinc in base to afford 2,2'-dichlorodi

phenylhydrazine Phenylhydrazine is the chemical compound with the formula . It is often abbreviated as . It is also found in edible mushrooms. Properties Phenylhydrazine forms monoclinic prisms that melt to an oil around room temperature which may turn yellow ...

. This intermediate undergoes the

benzidine rearrangement Benzidine ( trivial name), also called 1,1'- biphenyl-4,4'-diamine (systematic name), is an organic compound with the formula (C6H4NH2)2. It is an aromatic amine. It is a component of a test for cyanide. Related derivatives are used in the pro ...

to afford 3,3'-dichlorobenzidine. Aqueous solutions of 3,3'-dichlorobenzidine degrade in light to monochloro derivative. It undergoes chlorination (for example in water treatment plants) to give the tetrachloro derivative. The most widely practiced reaction of 3,3'-dichlorobenzidine is its double

diazotization Diazonium compounds or diazonium salts are a group of organic compounds sharing a common functional group where R can be any organic group, such as an alkyl or an aryl, and X is an inorganic or organic anion, such as a halide. The parent, compou ...

. This bis(diazo) intermediate is then coupled to derivatives of acetoacetylaminobenzene (CH₃C(O)CH₂C(O)NHAr). In this way, the diarylide commercial yellow pigments are produced: Pigment Yellow 12, Pigment Yellow 13, Pigment Yellow 14, Pigment Yellow 17, Pigment Orange 13, Pigment Yellow 81, and Pigment Yellow 83. PigYel12mainTaut

Safety

3,3'-Dichlorobenzidine is considered a

carcinogen A carcinogen () is any agent that promotes the development of cancer. Carcinogens can include synthetic chemicals, naturally occurring substances, physical agents such as ionizing and non-ionizing radiation, and biologic agents such as viruse ...

. This compound has been shown to increase the incidence of tumors in animals.3, 3'-Dichlorobenzidine
. U.S. Environmental Protection Agency, Integrated Risk Information System. 7 March 2011. Accessed 3 May 2011. Because it is structurally similar to

benzidine Benzidine (trivial name), also called 1,1'-biphenyl-4,4'-diamine (systematic name), is an organic compound with the chemical formula, formula (C6H4NH2)2. It is an aromatic amine. It is a component of a test for cyanide. Related derivatives are ...

, a known carcinogen, it is believed that it may share a similar mechanism in causing

bladder cancer Bladder cancer is the abnormal growth of cells in the bladder. These cells can grow to form a tumor, which eventually spreads, damaging the bladder and other organs. Most people with bladder cancer are diagnosed after noticing blood in thei ...

in humans.

References

External links

Spectrum Laboratories Chemical Fact Sheet
{{DEFAULTSORT:Dichlorobenzidine, 3,3'- Chlorobenzene derivatives IARC Group 2B carcinogens Anilines Biphenyls