2-(4-Aminophenyl)-1H-benzimidazol-5-amine
[CAS# 7621-86-5]

Identification

• Classification: Organic raw materials >> Heterocyclic compound >> Imidazoles
• Name: 2-(4-Aminophenyl)-1H-benzimidazol-5-amine
• Molecular Formula: C₁₃H₁₂N₄
• Molecular Weight: 224.26
• CAS Registry Number: 7621-86-5
• EC Number: 231-538-6
• SMILES: C1=CC(=CC=C1C2=NC3=C(N2)C=C(C=C3)N)N

Properties

• Density: 1.4±0.1 g/cm³ Calc.^*
• Melting point: 196 - 200 °C (Expl.)
• Boiling point: 545.5±56.0 °C 760 mmHg (Calc.)^*
• Flash point: 317.6±19.0 °C (Calc.)^*
• Index of refraction: 1.787 (Calc.)^*

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

Safety Data

• Hazard Symbols: GHS07;GHS08 Warning
• Risk Statements: H302-H312-H332-H341
• Safety Statements: P203-P261-P264-P270-P271-P280-P301+P317-P302+P352-P304+P340-P317-P318-P321-P330-P362+P364-P405-P501

Hazard Classification

Hazard	Class	Category Code	Hazard Statement
Acute toxicity	Acute Tox.	4	H302
Germ cell mutagenicity	Muta.	2	H341
Acute toxicity	Acute Tox.	4	H312
Acute toxicity	Acute Tox.	4	H332
Skin irritation	Skin Irrit.	2	H315
Skin sensitization	Skin Sens.	1B	H317
Specific target organ toxicity - repeated exposure	STOT RE	1	H372
Reproductive toxicity	Repr.	1B	H360
Chronic hazardous to the aquatic environment	Aquatic Chronic	3	H412
Eye irritation	Eye Irrit.	2	H319

Discovery and Applications

2-(4-Aminophenyl)-1H-benzimidazol-5-amine is an aromatic diamine with the molecular formula C₁₃H₁₁N₃. Structurally, it consists of a benzimidazole core substituted at the 2-position with a 4-aminophenyl group and at the 5-position of the benzimidazole ring with an amino group. This arrangement provides two nucleophilic amino groups attached to a rigid, fused heteroaromatic system, combining high reactivity with structural rigidity. The compound typically appears as a pale yellow solid, soluble in polar organic solvents such as dimethylformamide, dimethyl sulfoxide, and ethanol, but poorly soluble in water.

The compound is primarily used as a building block in polymer and materials chemistry. The amino groups can undergo condensation reactions with dianhydrides, diacid chlorides, or aldehydes to form polyimides, polyamides, Schiff bases, or other crosslinked networks. The fused benzimidazole structure contributes thermal stability, rigidity, and potential for hydrogen bonding, which is advantageous for designing high-performance polymers and materials with enhanced mechanical and thermal properties.

In addition to polymer synthesis, 2-(4-aminophenyl)-1H-benzimidazol-5-amine is used in the preparation of functional organic molecules and dyes. The aromatic amino groups allow for further functionalization via acylation, sulfonation, or other electrophilic substitutions, enabling the design of molecules with tailored optical, electronic, or chemical properties.

Synthetically, the compound can be prepared by the condensation of o-phenylenediamine derivatives with appropriate carboxylic acids or aldehydes to form the benzimidazole core, followed by selective introduction of the 4-aminophenyl substituent and amino group at the 5-position. Purification typically involves recrystallization or chromatographic techniques to ensure high purity suitable for polymerization or functionalization.

Overall, 2-(4-aminophenyl)-1H-benzimidazol-5-amine is a versatile diamine featuring a rigid heteroaromatic core with two reactive amino groups. Its combination of nucleophilicity, structural rigidity, and potential for further functionalization makes it valuable for high-performance polymers, functional materials, and advanced organic synthesis applications.

References

2022. Preparation of High-performance Polyimide Fibers with Wholly Rigid Structures Containing Benzobisoxazole Moieties. Chinese Journal of Polymer Science, 40(4).
DOI: 10.1007/s10118-022-2666-8