A simple computational approach for pKa calculation of organosulfur compounds

Abstract

The present work is related to predicting the pKa values of organosulfur compounds through the density functional theory (DFT). In this study, 22 organosulfur compounds were considered to calculate the theoretical pKa values. The main emphasis was given on the substitution of different groups on the sulfur atom. The computations were performed in the presence of dimethyl sulfoxide (DMSO) as solvent. Experimentally, the order of increase of acidity is; sulfides < sulfoxides < sulfones. The herein computed pKa values also follow the same order. The theoretical pKa values were computed using the DFT method B3LYP, with the basis sets 6-31G(d), 6-31+G(d,p) and the IEFPCM bulk solvation model. The majority of the pKa values computed through the diffuse function basis set were in excellent agreement with the experimental ones. Hence this computational approach, B3LYP/6-31+G(d,p)/IEFPCM, could be utilized to predict the pKa values of these types of organosulfur compounds.