2,5-Diaminotoluene sulfate
[CAS# 615-50-9]

Identification

• Classification: Organic raw materials >> Amino compound >> Acyclic monoamines, polyamines and their derivatives and salts
• Name: 2,5-Diaminotoluene sulfate
• Synonyms: 2,5-Toluenediamine sulfate; 2-Methyl-1,4-benzenediamine sulfate
• Molecular Formula: C₇H₁₀N₂^.H₂SO₄
• Molecular Weight: 220.24
• CAS Registry Number: 615-50-9
• EC Number: 210-431-8
• SMILES: CC1=C(C=CC(=C1)N)N.OS(=O)(=O)O

Properties

• Melting point: 300 ºC
• Water solubility: soluble

Safety Data

• Hazard Symbols: GHS06;GHS09 Danger
• Hazard Statements: H301:-H312:-H317:-H332:-H411:
• Precautionary 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	H332
Acute toxicity	Acute Tox.	4	H312
Chronic hazardous to the aquatic environment	Aquatic Chronic	2	H411
Skin sensitization	Skin Sens.	1	H317
Eye irritation	Eye Irrit.	2	H319
Specific target organ toxicity - repeated exposure	STOT RE	2	H373
Skin sensitization	Skin Sens.	1A	H317
Acute hazardous to the aquatic environment	Aquatic Acute	1	H400
Chronic hazardous to the aquatic environment	Aquatic Chronic	1	H410
Carcinogenicity	Carc.	2	H351

• Transport Information: UN 2811

Discovory and Applicatios

2,5-Diaminotoluene sulfate is a chemical compound consisting of 2,5-diaminotoluene in its sulfate salt form. The molecular structure includes a benzene ring substituted with amino groups (–NH₂) at the 2- and 5-positions and a methyl group (–CH₃) at the 1-position, forming 2,5-diaminotoluene. The sulfate is present as an acid salt, which increases the compound’s stability and water solubility compared to the free base form.

The synthesis of 2,5-diaminotoluene typically involves the reduction of 2,5-dinitrotoluene, a process carried out using catalytic hydrogenation or chemical reduction methods such as iron in acid or tin(II) chloride. After the reduction step, the resulting diamine is converted to its sulfate salt by treatment with sulfuric acid. This salt form is favored in commercial and industrial applications due to its improved handling properties and reduced volatility.

2,5-Diaminotoluene sulfate is widely used as a key intermediate in the manufacture of oxidative hair dyes. The diamine moieties participate in oxidation coupling reactions with other dye components, such as couplers and oxidants, to form colored azo or indamine compounds that provide permanent hair coloration. Its substitution pattern with amino groups at the 2- and 5-positions allows it to produce a range of colors, especially in the brown to reddish spectrum, depending on the specific formulation.

Beyond hair dye applications, 2,5-diaminotoluene sulfate is utilized in the synthesis of pigments, polymers, and pharmaceuticals where aromatic diamine functionality is required. The compound’s ability to undergo electrophilic substitution and form stable intermediates makes it valuable in organic synthesis for producing dyes, intermediates, and cross-linking agents.

The compound exhibits moderate solubility in water due to the sulfate salt form, which enhances its dissolution compared to the free diamine. Analytical techniques such as nuclear magnetic resonance (NMR) spectroscopy and infrared (IR) spectroscopy are employed to confirm the structure and purity of 2,5-diaminotoluene sulfate. High-performance liquid chromatography (HPLC) is commonly used for purity assessment and quality control in industrial production.

Safety considerations for 2,5-diaminotoluene sulfate align with those for aromatic amines, which can pose risks such as skin sensitization, irritation, and potential toxicity with prolonged exposure. The sulfate salt form is generally less volatile and easier to handle safely than the free amine, but protective measures such as gloves, eye protection, and adequate ventilation remain essential during use and processing.

In summary, 2,5-diaminotoluene sulfate is an important aromatic diamine sulfate salt primarily employed as an intermediate in permanent hair dye formulations. Its well-established synthesis from dinitrotoluene and functional versatility support its use in cosmetics, pigment production, and chemical synthesis. Comprehensive analytical methods and adherence to safety protocols ensure effective and safe utilization in industrial and commercial applications.

References

2020. Surface-enhanced Raman Scattering and X-ray Fluorescence Analyses of a Single Hair Colored with a Hair Dye Product. Analytical sciences : the international journal of the Japan Society for Analytical Chemistry.
DOI: 10.2116/analsci.20p144

2018. Eyebrow allergic contact dermatitis caused by m-aminophenol and toluene-2,5-diamine secondary to a temporary black henna tattoo. Contact Dermatitis, 78(5).
DOI: 10.1111/cod.12987

2017. Evaluation of concordance between labelling and content of 52 hair dye products: overview of the market of oxidative hair dye. European journal of dermatology : EJD, 27(2).
DOI: 10.1684/ejd.2016.2934