The hydrazinolysis of heterocyclic compounds. V. Reactions of 1-Amino-4,6-dimethylpyrimidin-2(1H)-one hydrazone in water

The cation of 1-amino-4,6-dimethylpyrimidin-2(1H)-one hydrazone (1) is stable in aqueous solutions. By contrast the neutral molecule species decomposes to yield 3,5-dimethylpyrazole (3) and 1-amino-4,6- dimethylpyrimidin-2(1H)-one (6) as major products, and 1,2,4-triazole-3,4,5-triamine (7) and other unidentified compounds as minor products. Covalent hydration and substituent effects in the cation species of (1) are discussed in seeking an explanation for anomalous ultraviolet spectra. Hydrogen deuterium exchange in methyl substituents is reported.