Synthesis, determination of p Ka values and GIAO NMR calculations of some new 3-alkyl-4-( p-methoxybenzoylamino)-4,5-dihydro-1 H-1,2,4-triazol-5-ones

Abstract

3-Alkyl-4-amino-4,5-dihydro-1 H-1,2,4-triazol-5-ones ( 2) reacted with p-methoxybenzoyl chloride to afford the corresponding 3-alkyl-4-( p-methoxybenzoylamino)-4,5-dihydro-1 H-1,2,4-triazol-5-ones ( 3). Five newly synthesized compounds have been characterized by elemental analyses, IR, 1H NMR, 13C NMR and UV spectral data. The newly synthesized compounds 3 were titrated potentiometrically with tetrabutylammonium hydroxide in four non-aqueous solvents such as acetonitrile, isopropyl alcohol, tert-butyl alcohol and N, N-dimethylformamide, and the half-neutralization potential values and the corresponding p K a values were determined for all cases. Thus, the effects of solvents and molecular structure upon acidity were investigated. In addition, isotropic 1H and 13C nuclear magnetic shielding constants of compounds 3 were obtained by the gauge-including-atomic-orbital (GIAO) method at the B3LYP density functional level. The geometry of each compound has been optimized using the 6-311G basis set. Theoretical values were compared to the experimental data.