Solvation Energy of Proton: a Consistent Calculation Schemefor Acid Dissociation Constantsand Standard Hydrogen Electrode Potentials

  • MATSUI Toru
    Graduate School of Pure and Applied Sciences, University of Tsukuba.Center for Computational Sciences, University of Tsukuba. 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8577, Japan
  • KIYAN Akane
    Graduate School of Pure and Applied Sciences, University of Tsukuba.Center for Computational Sciences, University of Tsukuba. 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8577, Japan
  • SHOJI Mitsuo
    Graduate School of Pure and Applied Sciences, University of Tsukuba.Center for Computational Sciences, University of Tsukuba. 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8577, Japan
  • SHIGETA Yasuteru
    Graduate School of Pure and Applied Sciences, University of Tsukuba.Center for Computational Sciences, University of Tsukuba. 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8577, Japan

Bibliographic Information

Other Title
  • プロトンの水和自由エネルギー: 酸解離定数および標準水素電極電位の高精度計算

Abstract

<p>We here review a scheme for estimating the acid dissociation constant (pKa) based on quantum-chemical calculations combined with a polarizable continuum model, where a parameter is determined for small reference molecules. This scheme enabled us to derive a semiquantitative pKa value of specific chemical groups and discuss the influence of the surroundings on the pKa values. As applications, we have derived the pKa value of the side chain of an amino acid and almost reproduced the experimental value. By using our computing schemes, we showed the influence of hydrogen bonds on the pKa values in the case of tripeptides, which decreases the pKa value by 3.0 units for serine in comparison with those of the corresponding monopeptides. The same procedure is also applicable to estimate the standard hydrogen electrode (SHE) potential in aqueous solution. With our computational scheme, the CCSD (T)/aug-cc-pVDZ method provides the SHE potential of 4.52 V, which is almost the same as the experimental SHE potential. This scheme also reproduces well the redox potentials of several typical reactions within almost 0.1 V. B3LYP also gives excellent redox potentials of the same reactions with almost the same accuracy with our new computational scheme.</p>

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