3-Alkyl(aryl)-4-amino4,5-dihydro-1H-1,2,4-triazol-5-ones (2) reacted with 4-methoxybenzaldehyde to afford the corresponding 3-alkyl (aryl)-4-(4-methoxybenzylideneamino)-4,5 dihydro-1H-1,2,4-triazol-5-ones (3). The newly synthesized 3 were titrated potentiometrically with tetrabutylammonium hydroxide in four nonaqueous solvents such as methyl alcohol, isopropyl alcohol, tert-butyl alcohol and N,N-dimethylformamide. The half-neutralization potential values and the corresponding pKa values were determined for all compounds synthesized in the solvents described above. Thus, the effects of solvents and molecular structure upon acidity were investigated. In addition, N-acetyl derivatives of 3 were also prepared. Fourteen new synthesized compounds in the study were fully characterized.