3,3'-Diaminobenzidine
[CAS# 91-95-2]

Identification

• Classification: Organic raw materials >> Amino compound >> Cycloalkylamines, aromatic monoamines, aromatic polyamines and derivatives and salts
• Name: 3,3'-Diaminobenzidine
• Synonyms: 3,3',4,4'-Biphenyltetramine; Biphenyl-3,3',4,4'-tetraamine
• Molecular Formula: C₁₂H₁₄N₄
• Molecular Weight: 214.27
• CAS Registry Number: 91-95-2
• EC Number: 202-110-6
• SMILES: C1=CC(=C(C=C1C2=CC(=C(C=C2)N)N)N)N

Properties

• Density: 1.3$+/-$0.1 g/cm³ Calc.^*
• Melting point: 172 - 176 $degree$C (Expl.)
• Boiling point: 481.7$+/-$45.0 $degree$C 760 mmHg (Calc.)^*
• Flash point: 282.7$+/-$25.6 $degree$C (Calc.)^*
• Solubility: water: 0.55 g/L (20 $degree$C) (Expl.)
• Index of refraction: 1.766 (Calc.)^*

^* Calculated using Advanced Chemistry Development (ACD/Labs) Software.

Safety Data

• Hazard Symbols: GHS08 Danger
• Risk Statements: H341-H350
• Safety Statements: P203-P280-P318-P405-P501

Hazard Classification

Hazard	Class	Category Code	Hazard Statement
Germ cell mutagenicity	Muta.	2	H341
Carcinogenicity	Carc.	1B	H350
Acute toxicity	Acute Tox.	4	H302
Eye irritation	Eye Irrit.	2	H319

Discovery and Applications

3,3'-Diaminobenzidine is an aromatic diamine compound consisting of two benzene rings connected by a single carbon–carbon bond at the 1-position, with amino groups substituted at the 3-position of each ring. This structural arrangement provides two nucleophilic amino groups in a symmetrical configuration, making the compound highly reactive and valuable as an intermediate in polymer chemistry, dye production, and analytical applications.

The molecular structure features a biphenyl core with amino groups at the meta positions on both rings. The amino groups serve as sites for condensation reactions with aldehydes, ketones, or diacid chlorides, enabling the formation of highly crosslinked polymers and resins. The biphenyl linkage contributes rigidity and planarity, while the positioning of the amino groups allows controlled reactivity in polymerization or coupling reactions.

Synthesis of 3,3'-diaminobenzidine typically involves the reduction of 3,3'-dinitrobenzidine using catalytic hydrogenation or chemical reducing agents under controlled conditions to convert nitro groups to amino groups. The reaction requires careful control of temperature and pH to avoid oxidation or polymerization of the intermediate, as the diamine is sensitive to air and light. Purification is essential to obtain a product suitable for industrial and laboratory use.

One of the main applications of 3,3'-diaminobenzidine is in the production of high-performance polymers, such as polyimides and epoxy resins. The diamine’s bifunctional nature allows polymer chains to extend and crosslink, producing materials with exceptional thermal stability, mechanical strength, and chemical resistance. These polymers are used in aerospace components, electronics, coatings, and adhesives, where durability under extreme conditions is required.

In addition to polymer applications, 3,3'-diaminobenzidine is used in dye and pigment production, particularly for the synthesis of azo dyes. Its amino groups can undergo diazotization and coupling reactions to form highly colored, stable compounds for textiles, inks, and analytical reagents. The diamine is also employed in immunohistochemistry and biochemical assays as a substrate for peroxidase enzymes, where it produces a colored precipitate used in detection and imaging applications.

Overall, 3,3'-diaminobenzidine is a versatile and reactive aromatic diamine. Its amino-functionalized biphenyl structure provides reactivity for polymer synthesis, dye chemistry, and analytical applications, making it an important intermediate in materials science, industrial chemistry, and biomedical research.

References

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2025. Lactate signalling leads to aggregation of immune-inflammatory hotspots and SLC5A12 blockade promotes their resolution. Nature Metabolism.
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