2,5-Diaminotoluene
[CAS# 95-70-5]

Identification

• Classification: Organic raw materials >> Amino compound
• Name: 2,5-Diaminotoluene
• Synonyms: 2-Methyl-1,4-benzenediamine; Toluene-2,5-diamine
• Molecular Formula: C₇H₁₀N₂
• Molecular Weight: 122.17
• CAS Registry Number: 95-70-5
• EC Number: 202-442-1
• SMILES: CC1=C(C=CC(=C1)N)N

Properties

• Density: 1.1±0.1 g/cm³ Calc.^*
• Melting point: 64 °C (Expl.)
• Boiling point: 273.7±20.0 °C 760 mmHg (Calc.)^*, 273.5 °C (Expl.)
• Flash point: 140.6±21.3 °C (Calc.)^*
• Index of refraction: 1.636 (Calc.)^*

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

Safety Data

• Hazard Symbols: GHS06;GHS09 Danger
• Risk Statements: H301-H312:-H317:-H332:-H411:
• Safety Statements: P261-P264-P270-P271-P272-P273-P280-P301+P316-P302+P352-P304+P340-P317-P321-P330-P333+P317-P362+P364-P391-P405-P501

Hazard Classification

Hazard	Class	Category Code	Hazard Statement
Acute toxicity	Acute Tox.	3	H301
Acute toxicity	Acute Tox.	4	H312
Acute toxicity	Acute Tox.	4	H332
Skin sensitization	Skin Sens.	1	H317
Chronic hazardous to the aquatic environment	Aquatic Chronic	2	H411
Eye irritation	Eye Irrit.	2	H319
Specific target organ toxicity - repeated exposure	STOT RE	2	H373
Acute hazardous to the aquatic environment	Aquatic Acute	1	H400
Serious eye damage	Eye Dam.	1	H318
Acute toxicity	Acute Tox.	3	H331
Skin sensitization	Skin Sens.	1A	H317
Chronic hazardous to the aquatic environment	Aquatic Chronic	1	H410

Discovery and Applications

2,5-Diaminotoluene is an aromatic organic compound characterized by a benzene ring substituted with two amino groups (–NH₂) at the 2- and 5-positions and a methyl group (–CH₃) at the 1-position, which corresponds to the toluene moiety. The molecular formula of this compound is C₇H₁₀N₂. It belongs to the class of diaminotoluenes, compounds notable for their use in dye and chemical industries.

The compound has been known and utilized since the early 20th century, especially due to its role as an intermediate in the manufacture of hair dyes and pigments. 2,5-Diaminotoluene is typically synthesized via the selective reduction or amination of dinitrotoluene derivatives or through nitration followed by catalytic hydrogenation of toluene-based precursors, allowing for the controlled introduction of amino groups at specific positions on the aromatic ring.

Its primary application is in the cosmetics industry, particularly as a key component in oxidative hair dye formulations. The presence of two amino groups facilitates its oxidation and coupling reactions with other dye precursors, producing a range of permanent hair colors. Compared to related compounds, 2,5-diaminotoluene offers advantageous color properties and reduced allergenic potential, which has made it a preferred ingredient in many commercial hair dye products.

Beyond hair dyes, 2,5-diaminotoluene is used in the synthesis of pigments, rubber chemicals, and certain pharmaceuticals. Its reactivity allows it to serve as a building block in the manufacture of azo dyes, which are widely employed for textile coloration due to their vivid and stable colors.

Analytical characterization of 2,5-diaminotoluene involves nuclear magnetic resonance (NMR) spectroscopy to confirm substitution patterns on the aromatic ring and the presence of amino and methyl groups. Infrared (IR) spectroscopy detects characteristic N–H stretching vibrations from the amino groups and aromatic C–H stretches. High-performance liquid chromatography (HPLC) and mass spectrometry (MS) are also utilized for purity assessment and molecular identification.

From a chemical safety perspective, 2,5-diaminotoluene should be handled with caution as aromatic amines may present toxicity and sensitization risks. Protective measures include the use of gloves, eye protection, and adequate ventilation to prevent inhalation of dust or vapors. Regulatory guidelines often limit its concentration in consumer products to minimize health risks.

In summary, 2,5-diaminotoluene is a well-established aromatic diamine primarily employed in hair dye formulations and pigment synthesis. Its selective synthesis routes, functional versatility, and analytical methods support its widespread industrial application, while adherence to safety protocols ensures responsible handling in manufacturing and product use.

References

2023. Haarfärbemittel verursachen Kontaktdermatitis. Allergo Journal.
DOI: 10.1007/s15007-023-5837-1

2021. Common Allergens. Clinical Contact Dermatitis.
DOI: 10.1007/978-3-030-49332-5_22

2020. Contact Allergy to Hair Dyes. Contact Dermatitis.
DOI: 10.1007/978-3-030-36335-2_90