Hybrid QM/MM molecular dynamics simulations for an ionic SN2 reaction in the supercritical water: OH- + CH3Cl → CH3OH + Cl-

Takumi Hori, Hideaki Takahashi, Tomoshige Nitta

Research output: Contribution to journalArticle

22 Citations (Scopus)

Abstract

A hybrid real space quantum mechanical/molecular mechanical (RS-QM/MM) method has been applied to an ionic SN2 reaction (OH- + CH3Cl → CH3OH + Cl-) in water solution to investigate dynamic solvation effects of the supercritical water (SCW) on the reaction. It has been demonstrated that the approaching process of OH- to methyl group is prevented by water molecules in the ambient water (AW), while the reaction takes place easily in the gas phase. Almost the same solvation effect on the dynamics of OH- is observed in the SCW, though the bulk density of water is substantially reduced compared with that of the AW. It has been shown that the solvation of the SCW around the OH anion is locally identical to that of the AW due to the strong ion-dipole interactions between OH- and water molecules. At the transition state, the QM/MM simulations have revealed that the excess electron is quite flexible, and the charge volume, as well as the fractional charges on atoms, vary seriously depending on the instantaneous solvent configurations. However, it has been found that the solvation energy in the SCW can be qualitatively related to the HOMO volume of the system by Born's equation.

Original languageEnglish
Pages (from-to)209-221
Number of pages13
JournalJournal of Computational Chemistry
Volume24
Issue number2
DOIs
Publication statusPublished - 2003 Jan 30
Externally publishedYes

Keywords

  • Density functional theory
  • Hybrid quantum mechanical/molecular mechanical method
  • Real space grids
  • S2 reaction
  • Supercritical water

ASJC Scopus subject areas

  • Chemistry(all)
  • Computational Mathematics

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