Determination of pKa for substituted benzoic acids in mixed solvent using density functional theory and QSPR

摘要

The pKa of some substituted benzoic acid were calculated using three different methods in 50% ethanol/water at 273.15 K with B3LYP/6-31G(d,p) level of calculations. The calculated pKas were compared with the experimental values. The quantitative structure property relationship was found to give good results compared with the first principle methods. The solution-phase quantum chemical descriptors were found to give more accurate pKas than the gas-phase descriptors. The participation of quantum chemical descriptors as bond lengths and charge density mainly affects the acidity constant of studied compounds as represented by high correlation coefficient factors for the obtained equations. The obtained equations were applied to predict the acidity constant of some related structures to benzoic acid.