Nine new 3-alkyl(aryl)-4-(3-methoxy-4-cinnamoyloxy)benzylideneamino-4,5-dihydro-1H-1,2,4-triazol-5-ones (4) were synthesized by the reactions of 3-alkyl(aryl)-4-amino-4,5-dihydro-1H-1,2,4-triazol-5-ones (2) with 3-methoxy-4-cinnamoyloxybenzaldehyde (3). The structures of new nine compounds were established from IR, ¹H-NMR, ¹³C-NMR and UV spectral data. The synthesized compounds were analyzed for their in vitro potential antioxidant activities in three different methods. In addition, to investigate the effects of solvents and molecular structure upon acidity compounds 4 were titrated potentiometrically with tetrabutylammonium hydroxide in four non-aqueous solvents (isopropyl alcohol, tert-butyl alcohol, acetone and N,N-dimethylformamide).

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