Studies on acidity behaviours of some benzimidazole derivative compounds

In this study, four number (Phenyl[2-(2-bromobenzyl)-1H-1,3-benzimidazol-5-yl]methanone (1), Phenyl[2-(2-fluorobenzyl)-1H-1,3-benzimidazole-5-yl]methanone (2), Phenyl[2-(2-chlorobenzyl)-1H-1,3-benzimidazol-5-yl]methanone (3) and Phenyl[2-(2-methylbenzyl)-1H-1,3-benzimidazol-5-yl]methanone (4)] benzimidazole derivative compounds were calculated enthalpy (ΔHo) and entropies (ΔSo) by a computer program MOPAC 2012 using semi-empirical quantum chemical methods (AM1, MNDO, MNDOD, PM3, PM6, PM6-DH2, PM7 ve RM1) after completed the geometric optimization of molecules in eleven different solvent (Water, Ethanol, Methanol, N-Propanol, 2-Propanol, N-Butanol, Tert-Butanol, Ethylene Glycol, N,N-Dimethylformamide (DMF), Dimethyl Sulfoxide (DMSO) and Acetonitrile) phase. Acidity constants (pKa) values of each compound were calculated with the aid of the obtained values. The pKa values found as theoretically have been investigated parallels between the experimental data. The results of the calculations are found to give suitable results of the calculations made with semi-empirical quantum chemical methods.