First-principles determination of the absolute hydration free energy of the hydroxide ion

Chang Guo Zhan, David A. Dixon

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117 Scopus citations

Abstract

The absolute hydration free energy of the hydroxide ion, ΔGhyd298(HO-), a fundamental quantity in solution chemistry, has "experimental" values ranging from -90.6 to -110.0 kcal/mol. We report a first-principles determination of ΔGhyd298(HO-) by using a reliable computational protocol of high-level first-principles supermolecule-continuum calculations, the same approach recently used to determine the absolute hydration free energy of the proton. In the supermolecule-continuum approach, part of the solvent surrounding the solute is treated quantum mechanically, and the remaining bulk solvent is approximated by a dielectric continuum medium accounted for by a recently developed self-consistent reaction field model known as surface and volume polarization for electrostatic interaction (SVPE) or the fully polarizable continuum model (FPCM). With this approach, the calculated results can systematically be improved by increasing the number of quantum mechanically treated solvent molecules, and ΔGhyd298(HO-) is accurately predicted to be -104.5 kcal/mol. The ΔGhyd298(HO-) value of -104.5 kcal/mol, combined with our previously determined ΔGhyd298(H+) value of -262.4 kcal/mol, allows the prediction of the sum of absolute hydration free energies of the proton and hydroxide to be -366.9 kcal/mol, in excellent agreement with the well-established experimental thermodynamic value of -366.6 ± 0.1 kcal/mol.

Original languageEnglish
Pages (from-to)9737-9744
Number of pages8
JournalJournal of Physical Chemistry A
Volume106
Issue number42
DOIs
StatePublished - Oct 24 2002

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry

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