Microwave-assisted synthesis of some 1, 2, 4-triazol-3-ones and potentiometric determination of their pKa in amfiprotic and dipolar aprotic-water mixtures

Abstract

The novel 5-alkyl(aryl)-4-(aryl)-2, 4-dihydro-3H-1, 2, 4-triazol-3-ones (1-12) were synthesized by reaction of (N?-ethoxycarbonyl)-4-alkyl(aryl)hydrazonic acid ethyl ester with primary amines by microwave irradiation. Stoichiometric protonation constants of 1-12 were determined potentiometrically in 50% (v/v) amfiprotic (ethanol and methanol) and dipolar aprotic (dioxan)-water mixtures at 25°C with an ionic strength of 0.10 M. The calculation of the stoichiometric protonation constants was carried out using a PKAS computer program. The effects of solvents composition on the stoichiometric protonation constants are discussed.