Dependence of pK(a) on solute cavity for diprotic and triprotic acids

作者：Lee Tae Bum^*; Mckee Michael L

来源：Physical Chemistry Chemical Physics, 2011, 13(21): 10258-10269.

DOI：10.1039/c1cp20161a

A systematic study of Delta G(aq)/pK(a) for monoprotic, diprotic, and triprotic acids has been carried out based on DFT/aug-cc-pVTZ combined with CPCM and SMD solvation modeling. All DFT/cavity set combinations considered showed similar accuracy for Delta G(aq)(1)/pK(a1) (70% within +/-2.5 kcal mol(-1) of experiment) while only the M05-2X/Pauling cavity combination gave reasonable results for Delta G(aq)(2)/pK(a2) when both pK(a) values are separated by more than three units (70% within +/-5.0 kcal mol(-1) of experiment). The choice of experimental data is critical to the interpretation of the calculated accuracy especially for several inorganic acids. For the calculation of Delta G(aq)(3)/pK(a3), the larger experimental uncertainty and an unrealistic orbital population of diffuse function for trianions in the gas phase hinders an evaluation of the predictive performance. We find the M05-2X functional with the Pauling cavity set is the best choice for Delta G(aq)(2)/pK(a2) prediction in aqueous media while all DFT/cavity sets considered were competitive for Delta G(aq)(1)/pK(a1).

• 出版日期2011