3,3'-Dichlorobenzidine

3,3'-Dichlorobenzidine is an organic compound 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.^[3] Its use in the production of dyes has been largely discontinued because of concerns about carcinogenicity.

3,3'-Dichlorobenzidine^[1]

Names
Preferred IUPAC name 3,3′-Dichloro[1,1′-biphenyl]-4,4′-diamine
Other names 4-(4-Amino-3-chlorophenyl)-2-chloroaniline 4,4′-Diamino-3,3′-dichlorobiphenyl o,o'-Dichlorobenzidine 3,3′-Dichlorobiphenyl-4,4′-diamine 3,3′-Dichloro-4,4′-biphenyldiamine 3,3′-Dichloro-4,4′-diaminobiphenyl
Identifiers
CAS Number	91-94-1 Y
3D model (JSmol)	Interactive image
ChEMBL	ChEMBL314470 Y
ChemSpider	6803 Y
ECHA InfoCard	100.001.918
KEGG	C19225 Y
PubChem CID	7070
UNII	1SDI2328UX Y
CompTox Dashboard (EPA)	DTXSID6020432
InChI InChI=1S/C12H10Cl2N2/c13-9-5-7(1-3-11(9)15)8-2-4-12(16)10(14)6-8/h1-6H,15-16H2 Y Key: HUWXDEQWWKGHRV-UHFFFAOYSA-N Y InChI=1/C12H10Cl2N2/c13-9-5-7(1-3-11(9)15)8-2-4-12(16)10(14)6-8/h1-6H,15-16H2 Key: HUWXDEQWWKGHRV-UHFFFAOYAF
SMILES Clc2cc(c1ccc(N)c(Cl)c1)ccc2N
Properties
Chemical formula	C12H10Cl2N2
Molar mass	253.13 g/mol
Appearance	Gray or purple crystalline solid
Melting point	132 to 133 °C (270 to 271 °F; 405 to 406 K)
Boiling point	402 °C (756 °F; 675 K)
Solubility in water	0.07% (15°C)[2]
Hazards
Occupational safety and health (OHS/OSH):
Main hazards	Potential carcinogen[2]
NIOSH (US health exposure limits):
PEL (Permissible)	carcinogen[2]
REL (Recommended)	Ca[2]
IDLH (Immediate danger)	Ca [N.D.][2]
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Y verify (what is YN ?) Infobox references

Preparation and reactions

3,3'-Dichlorobenzidine is prepared in two steps from 2-nitrochlorobenzene. The first step involves reduction with zinc in base to afford 2,2'-dichlorodiphenylhydrazine. This intermediate undergoes the benzidine rearrangement to afford 3,3'-dichlorobenzidine.^[4]

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. 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.^[3]

Structure of Pigment Yellow 12, which is derived from dichlorobenzidine.^[5]

Safety

3,3'-Dichlorobenzidine is considered a carcinogen.^[1] This compound has been shown to increase the incidence of tumors in animals.^[6] Because it is structurally similar to benzidine, a known carcinogen, it is believed that it may share a similar mechanism in causing bladder cancer in humans.^[6]