2,2'-Dimethyl[1,1'-biphenyl]-4,4'-diamine
[CAS# 84-67-3]

Identification

• Classification: Organic raw materials >> Aryl compounds >> Biphenyl compounds
• Name: 2,2'-Dimethyl[1,1'-biphenyl]-4,4'-diamine
• Synonyms: 2,2'-Dimethyl-4,4'-diaminobiphenyl; 2,2'-Dimethylbenzidine; 2,2'-Tolidine; 4,4'-Diamino-2,2'-dimethylbiphenyl; m-Tolidine
• Molecular Formula: C₁₄H₁₆N₂
• Molecular Weight: 212.29
• CAS Registry Number: 84-67-3
• EC Number: 201-551-1
• SMILES: CC1=C(C=CC(=C1)N)C2=C(C=C(C=C2)N)C

Properties

• Density: 1.1$+/-$0.1 g/cm³ Calc.^*, 1.106 g/mL (Expl.)
• Melting point: 105-106 $degree$C (Expl.)
• Boiling point: 344.4$+/-$37.0 $degree$C 760 mmHg (Calc.)^*
• Flash point: 192.9$+/-$26.0 $degree$C (Calc.)^*
• Index of refraction: 1.638 (Calc.)^*

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

Safety Data

• Hazard Symbols: GHS07 Warning
• Risk Statements: H302
• Safety Statements: P264-P270-P301+P317-P330-P501

Hazard Classification

Hazard	Class	Category Code	Hazard Statement
Acute toxicity	Acute Tox.	4	H302
Skin irritation	Skin Irrit.	2	H315
Eye irritation	Eye Irrit.	2	H319

Discovery and Applications

2,2'-Dimethyl[1,1'-biphenyl]-4,4'-diamine is an aromatic diamine compound in which two benzene rings are connected via a single carbon–carbon bond at the 1-position of each ring, forming a biphenyl structure. Each benzene ring bears a primary amino group at the para (4-) position, and methyl groups are substituted at the 2-position of both rings. This combination of amino and methyl substituents on a biphenyl scaffold provides both chemical reactivity and steric effects, making the compound an important intermediate in polymer chemistry and materials science.

The molecular structure consists of a biphenyl core with para-amino groups and ortho-methyl groups on each ring. The amino groups serve as nucleophilic sites for condensation reactions with diacid chlorides, dianhydrides, or epoxides, enabling the formation of high-performance polymers such as polyamides, polyimides, and epoxy resins. The ortho-methyl groups introduce steric hindrance, which can influence polymer chain packing, solubility, and mechanical properties. The biphenyl linkage contributes rigidity and thermal stability to the resulting materials.

Synthesis of 2,2'-dimethyl[1,1'-biphenyl]-4,4'-diamine generally involves the coupling of appropriately substituted halobenzenes through palladium-catalyzed cross-coupling reactions, followed by nitration and reduction to convert nitro groups into amino groups. Careful control of reaction conditions is necessary to prevent overreaction or undesired side products, ensuring a high-purity diamine suitable for polymerization.

The primary application of this compound is in the production of high-performance polymers. Its bifunctional amino groups allow polymer chains to grow in a controlled manner, while the biphenyl core and ortho-methyl substituents provide thermal resistance, rigidity, and dimensional stability. Polymers derived from this diamine are used in aerospace components, electronic materials, adhesives, coatings, and composite structures, particularly where heat resistance and mechanical strength are required.

In addition to polymer applications, 2,2'-dimethyl[1,1'-biphenyl]-4,4'-diamine can serve as a building block in the synthesis of dyes, pigments, and functionalized aromatic molecules. Its amino groups allow selective chemical transformations, and the biphenyl framework contributes rigidity and electronic properties that are valuable in specialty chemical synthesis.

Overall, 2,2'-dimethyl[1,1'-biphenyl]-4,4'-diamine is a versatile aromatic diamine with nucleophilic amino groups and sterically significant methyl substituents on a rigid biphenyl scaffold. Its structural features make it a critical intermediate for high-performance polymers, epoxy resins, and specialty chemical synthesis.

References

2023. Structural tailoring of covalent organic frameworks with steric effects. Science China Chemistry.
DOI: 10.1007/s11426-023-1694-2

2023. Development of polyimide aerogel stock shapes through polyimide aerogel particles. Journal of Porous Materials.
DOI: 10.1007/s10934-023-01489-1

2023. Isocyanate-Derived Aerogels and Nanostructure–Materials Properties Relationships. Springer Handbook of Aerogels.