Preparation, Characterization, and Potentiometric Titrations of Some New Di-[3-(3-alkyl/aryl-4,5-dihydro-1H-1,2,4-triazol-5-one-4-yl)-azomethinphenyl] isophthalate/terephthalate Derivatives


Abstract: 3-Alkyl(Aryl)-4-amino-4,5-dihydro-1H-1,2,4-triazol-5-ones (2) reacted with di-(3-formylphenyl) isophthalate (3) and di-(3-formylphenyl) terephthalate (6) to afford the corresponding 6 novel di-[3-(3-alkyl/aryl-4,5-dihydro-1H-1,2,4-triazol-5-one-4-yl)- azomethinphenyl] isophthalates (4) and 6 novel di-[3-(3-alkyl/aryl-4,5- dihydro-1H-1,2,4-triazol-5-one-4-yl)-azomethinphenyl] terephthalates (7), respectively. The acetylation reactions of compounds 4 and 7 were investigated, and 5 and 8 type compounds were obtained, respectively. The new compounds synthesized were characterized by using IR, ^1H-NMR, ^{13}C-NMR, and UV spectral data together with elemental analysis. In addition, to investigate the effects of solvents and molecular structure upon acidity, compounds 4 and 7 were titrated potentiometrically with tetrabutylammonium hydroxide in 5 non-aqueous solvents (isopropyl alcohol, tert-butyl alcohol, N,N-dimethylformamide, acetone, and dimethyl sulfoxide). The half-neutralization potential values and the corresponding pK_a values were determined for all cases.

Keywords: 4,5-Dihydro-1H-1,2,4-triazol-5-one, Schiff base, acidity, potentiometric titration, acetylation.

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