Synthesis and antioxidant activities of some new 4-(4-hydroxybenzylidenamino)-4,5-dihydro-1H-1,2,4-triazol-5-one derivatives with their acidic properties

Fourteen new compounds having 4,5-dihydro-1H-1,2,4-triazol-5-one ring, namely six new 3-alkyl(aryl)-4-(4-hydroxybenzylidenamino)-4,5dihydro-1H-1,2,4-triazol-5-ones (3), four new 1-acetyl-3-alkyl(aryl)-4-(4acetyloxybenzylidenamino)-4,5-dihydro-1H-1,2,4-triazol-5-ones (4), two new 1-methyl-3-alkyl-4-(4-methoxybenzylidenamino)-4,5-dihydro-1H-1,2,4-triazol-5-ones (5) and two new 3-alkyl(aryl)-4-[4-(p-tolylsulfonyl)oxybenzylidenamino]-4,5-dihydro-1H-1,2,4-triazol-5-ones (6), were synthesized. The structures of the newly synthesized compounds were determined by elemental analysis as well as IR, H-1 NMR, C-13 NMR and UV spectral data and their antioxidant activities, except compounds 3e and 4f, were investigated. In addition, compounds 3a-f were titrated potentiometrically with tetrabutylammonium hydroxide in three non-aqueous solvents such as isopropyl alcohol, t-butyl alcohol and N,N-dimethyl formamide. The half-neutralization potential values and the corresponding pK(a) values were determined for all the cases.