Quantum chemical modeling of ions in solution can be challenging, as continuum solvent models often produce inaccurate ?Gsolv values for ions.  The calculation of pKa values provides a convenient means to compare the results of continuum solvent models to experimental values.  Previous studies have shown that predicted pKa values in water generally do not match the experimental values well.  In the interest of choosing a solvation model for use in modeling an organic reaction mechanism involving anions, pKa and ?G*solv values for solvation in methanol were calculated and compared to available experimental values, to gauge accuracy of the solvation models. In addition, different thermodynamic cycles, density functionals and basis sets were employed, in an attempt to determine a method which produces accurate results without the use of empirical corrections.  It was found that calculated pKa values in methanol are generally closer to the experimental values than are the corresponding aqueous pKa values, and that the SM8 model shows a great deal of promise in modeling solvent effects in reactions involving anions.

DFT calculations of pKa values in methanol in different continuum solvation models: Avoiding empirical corrections

246th National Meeting (2013)

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