3,3'-Dichlorobenzidine is an

organic compound In chemistry, organic compounds are generally any chemical compounds that contain carbon-hydrogen or carbon-carbon bonds. Due to carbon's ability to catenate (form chains with other carbon atoms), millions of organic compounds are known. The ...

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.Gerald Booth, "Nitro Compounds, Aromatic" in ''Ullmann's Encyclopedia of Industrial Chemistry'', Wiley-VCH: Weinheim, 2005. ...

. 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 produc ...

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. General properti ...

. This bis(diazo) intermediate is then coupled to derivatives of acetoacetylaminobenzene (CH₃C(O)CH₂C(O)NHAr). In this way, the following commercial yellow pigments are produced:

pigment Yellow 12 Pigment Yellow 12 is an organic compound and an azo compound. It is a widely used yellow pigment. It is also classified as a diarylide pigment, being derived from 3,3'-dichlorobenzidine. It is closely related to Pigment Yellow 13, wherein the t ...

, pigment Yellow 13,

pigment Yellow 14 A pigment is a colored material that is completely or nearly insoluble in water. In contrast, dyes are typically soluble, at least at some stage in their use. Generally dyes are often organic compounds whereas pigments are often inorganic compoun ...

, pigment Yellow 17 and pigment Yellow 83. PigmentYellow12corrected

Safety

3,3'-Dichlorobenzidine is considered a

carcinogen A carcinogen is any substance, radionuclide, or radiation that promotes carcinogenesis (the formation of cancer). This may be due to the ability to damage the genome or to the disruption of cellular metabolic processes. Several radioactive substan ...

. This compound has been shown to increase the incidence of tumors in animals.3, 3'-Dichlorobenzidine
.

U.S. Environmental Protection Agency The Environmental Protection Agency (EPA) is an independent executive agency of the United States federal government tasked with environmental protection matters. President Richard Nixon proposed the establishment of EPA on July 9, 1970; it be ...

, 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 formula (C6H4NH2)2. It is an aromatic amine. It is a component of a test for cyanide. Related derivatives are used in the produc ...

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

bladder cancer Bladder cancer is any of several types of cancer arising from the tissues of the urinary bladder. Symptoms include blood in the urine, pain with urination, and low back pain. It is caused when epithelial cells that line the bladder become mali ...

in humans.

References

External links

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