Theoretical Study on the Mechanism of Halogen Exchange Reaction of Alkyl Halide in Aqueous Solution

DOI

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Other Title
  • 水溶液中におけるハロゲン化アルキルのハロゲン交換反応のメカニズムについての量子化学的研究

Description

The aim of our study is to elucidate the difference in the reaction mechanisms, SN1 and SN2, from the standpoint of quantum chemistry. In the SN1 mechanism, the first step is a slow ionization of the substrate and the second is a rapid reaction between the intermediate carbocation and the nucleophile. The ionization is always assisted by the solvent. Therefore, the existence of the solvent molecules is essential to the SN1 type reaction. We have carried out the ab initio MO calculations for alkyl halide/halide substitution reactions, Cl-CR3 + Cl- (R=H or CH3), in the gas-phase and also in aqueous solution. In the gas-phase calculations, it was found that the variations of molecular orbitals along the reaction processes depend on the numbers of methyl substitution. We have obtained the free energy profiles in aqueous solution, using the statistical perturbation method based on Monte Carlo simulation with QM/MM method. The solute molecules are treated as QM (ab initio MO), and 100 water molecules (solvent molecules) are treated as MM (TIP3P). The calculated activation free energy of the halide substitution reaction of methylchloride is higher in water than in gas-phase.

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Details 詳細情報について

  • CRID
    1390001205554607232
  • NII Article ID
    130005011317
  • DOI
    10.11494/kisoyuki.53.0.47.0
  • Data Source
    • JaLC
    • CiNii Articles
  • Abstract License Flag
    Disallowed

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