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3,3'-Diaminobenzidine

3,3'-Diaminobenzidine
Skeletal formula of 3,3'-Diaminobenzidine
Ball-and-stick model of the 3,3'-diaminobenzidine molecule
Names
Preferred IUPAC name
[1,1'-Biphenyl]-3,3',4,4'-tetramine
Other names
[1,1'-Biphenyl]-3,3',4,4'-tetraamine (not recommended)
3,3',4,4'-Biphenyltetramine
3,3',4,4'-Tetraamino-diphenyl
Identifiers
3D model (JSmol)
1212988
ChEBI
ChEMBL
ChemSpider
ECHA InfoCard 100.001.919
EC Number 202-110-6
PubChem CID
RTECS number DV8750000
DV8753000 (4HCl)
UNII
UN number 2811
Properties
C12H14N4
C12H18Cl4N4 (4HCl)
Molar mass 214.27 g/mol
360.11 g/mol (4HCl)
Melting point 175 to 177 °C (347 to 351 °F; 448 to 450 K) (280 °C for 4HCl.2H2O)
Hazards
Safety data sheet External MSDS
GHS pictograms The health hazard pictogram in the Globally Harmonized System of Classification and Labelling of Chemicals (GHS)
GHS signal word Danger
H341, H350
P201, P202, P281, P308+313, P405, P501
NFPA 704
Flammability code 1: Must be pre-heated before ignition can occur. Flash point over 93 °C (200 °F). E.g., canola oil Health code 2: Intense or continued but not chronic exposure could cause temporary incapacitation or possible residual injury. E.g., chloroform Reactivity code 2: Undergoes violent chemical change at elevated temperatures and pressures, reacts violently with water, or may form explosive mixtures with water. E.g., phosphorus Special hazards (white): no codeNFPA 704 four-colored diamond
Lethal dose or concentration (LD, LC):
LD50 (median dose)
 mouse, oral Acute: 1834 mg/kg.
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
No  (what is YesYNo ?)
Infobox references

3,3'-Diaminobenzidine (DAB) is an organic compound with the formula (C6H3(NH2)2)2. This derivative of benzidine is a precursor to polybenzimidazole, which forms fibers that are renowned for their chemical and thermal stability. As its water-soluble tetrahydrochloride, DAB has been used in of nucleic acids and proteins.

DAB is symmetric about the central carbon bond between both ring structures. In the crystal, the rings of each molecule are co-planar and the amine units connect molecules to form an intermolecular 3-dimensional hydrogen bond network.

Diaminobenzidine, which is commercially available, is prepared by treating 3,3'-dichlorobenzidine with ammonia with a copper catalyst at high temperature and pressure, followed by acidic workup.

An alternate synthesis route involves the diacylation of benzidine with acetic anhydride under basic conditions:

The diacetylated compound then undergoes nitration with nitric acid to produce an ortho-dinitro compound due to the ortho-directing acetyl substituents:

The acetyl groups are then removed through saponification:

The dinitrobenzidine compound is then reduced with hydrochloric acid and iron to produce 3,3'-diaminobenzidine:

The reduction of the dinitrobenzidine compound can also proceed with tin(II) chloride instead of iron powder or with sodium dithionite in methanol.


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