Structure and polarographic behavior of 1-hexyl- and 1-phenyl-4-hydroxyimino-3-methyl-4,5-dihydropyrazol-5-ones

Polarographic behavior of 1-hexyl- and 1-phenyl-4-hydroxyimino-3-methyl-4,5 -dihydropyrazol-5-ones was studied in aqueous 2-propanol in the pH range fr om 2 to 12, and the origin of the limiting current was established. The ele ctronic structure of the compounds and cations and anions derived therefrom was calculated by the MNDO method. Products of electrochemical reduction a t different pH values were isolated and identified. In weakly acidic medium 1-hexyl-4-hydroxyimino-3-methyl-4,5-dihydropyrazol-5-one is reduced to 4,4 '-azobis(1-hexyl-5-hydroxy-3-methylpyrazole), and in alkaline medium the re duction product is 4-amino-1-hexyl-5-hydroxy-3-methylpyrazole which is oxid ized to 4,4'-azobis(1-hexyl-5-hydroxy-3-methylpyrazole) (pH 9.6) or 1-hexyl -3-methyl-4,5-dihydropyrazole-4,5-dione (pH 11.6) on exposure to air.