Calculations of pK_a values of carboxylic acids in aqueous solution using density functional theory

摘要

With the specific aim of calculating the acidity equilibrium constant (K_a) of carboxylic acids in aqueous solution we investigated the solute-solvent interactions of these acids and their corresponding anions.The pK_a (-lgK_a) values have been calculated using density functional theory (DFT).The polarized continuum model (PCM) is used to describe the solvent.Using these methods,we successfully predicted the pK_as of 66 carboxylic acids in aqueous with the average error of 0.5 in pK_a units.Two different thermodynamic cycles have been studied.The theoretical values are in better agreement with the experimental results for those acids with moderate strength of acidity with the pK_a value higher than 3.