Synthesis of 4-Amino-3,5-dimethyl-l,2,4-triazole

Hydrazinium hydrazine carboxylate is used in the preparation of 4-amino-3,5-dimethyl-l,2,4-triazole, a useful compound in agriculture and medicine. When a mixture of viscous liquid hydrazinium hydrazine carboxylate and acetonitrile is kept at room temperature, two layers appear the top layer being acetonitrile and the lower one N2H5COON2H3. A pink color develops in the acetonitrile layer after about 12 h. After two to three weeks, a white crystalline compound is formed in the hydrazinium hydrazine carboxylate layer, and the pinkish acetonitrile layer disappears. The white crystals are those of 4-amino-3,5-dimethyl-l,2,4-triazole. 

The synthesis of 4-amino-3,5-dimethyl-l,2,4-triazole is also carried out using hydrazinium hydrazine carboxylate as the starting material it is boiled under reflux with acetonitrile (20 ml) for 4h [5]. The resultant solution is evaporated over a water bath to afford colorless crystals of the triazole. The crystals are separated by filtration and washed with a small amount of acetone followed by acetonitrile, and then dried in air to give the product (1.3 g). The compound is freely soluble in DMSO and water, slightly soluble in acetone, and insoluble in benzene, carbon tetrachloride, chloroform, and acetonitrile. 

The solid compound has been characterized by elemental analysis, infrared and NMR ( H and spectroscopy, and X-ray diffraction. The analytical and spectral data confirm that the compound is 4-amino-3,5-dimethyl-1,2,4-triazole. The mass spectral fragmentation pattern has been successfully interpreted on the basis of its structure. 

Hydrazine or its salts are known to form amidrazone salts (1) by nucleophilic attack on acetonitrile. Compound 2 (4-amino-3,5-dimethyl-1,2,4-triazole) appears to be formed through six-membered ring 

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Vittal, J.J., Angadi, V.B., and Patil, K.C. (1989) Reactivity of hydrazinium hydrazi-necarboxylate-synthesis of 4-amino-3,5-dimethyl-l,2,4-triazole. Journal of the Indian Institute of Science, 69, 119-124. 

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