Solvent and moleculer structure effects on acidity strength in non-aqueous medium

The acidic properties of ten 3-alkyl(aryl)-4-[3-hydroxy-4-methoxy benzylidenamino]-4,5-dihydro-1H-1,2,4-triazol-5-one derivatives were investigated. In this study, isopropyl alcohol and tert‐butanol were used as an amphiprotic solvent. Aceton and N,N‐ dimethylformamide (DMF) were preferred as a dipolar aprotic solvent. Compounds were titrated with tetrabuthylamonnium hydroxide (TBAH) in isopropyl alcohol and titrimetric analyses were used potentiometric method determining the end-points, half-neutralization method determining acidity. Typical S-shaped titration graphs excepted were determined. The acidity strengths of 4,5-dihydro-1H-1,2,4-triazol-5-one derivatives in amphiprotic and dipolar aprotic solvents were calculated using tables and graphs. The pKa values obtained in the solvents were found to be differentiated. The effects of solvent, molecular structure, autoprotolysis constant dielectric constant, and leveling‐differentiation effects of the solvents upon acidity strength of the compounds were discussed.