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Determination And QSAR Study Of The Dissociation Constants Of Some 4,5-Disubsituted-2,4-Dihydro-3H-1,2,4-Triazoline-3-Thiones

Vesna Dimova, Nada Perisic-Janjic

A number of 4,5-disubstituted-2, 4-dihydro-3H-1,2,4-triazoline-3-thiones were obtained by the cyclization of the appropriate thiosemicarbazides. The behavior of newly synthesized 1,2,4-triazole derivatives in aqueous NaOH solutions was studied at room temperature using the method of UV-VIS spectroscopy. The investigated compounds have two dissociation processes. The first process belongs to the dissociation of -SH proton; the second dissociation process is dissociation of phenolic -OH group. QSAR study on dissociation constant has been made using the Hansch and Free - Willson approach. The pKa values(dissociation of -SH andOH group) were correlated with structure using various physicochemical(electronic, steric and hydrophobic) parameters.