Hybrid QM/MM molecular dynamics simulations for an ionic SN2 reaction in the supercritical water: OH− + CH3Cl → CH3OH + Cl−
Hybrid QM/MM molecular dynamics simulations for an ionic SN2 reaction in the supercritical water: OH− + CH3Cl → CH3OH + Cl−
复制标题
超临界水中离子 SN2 反应的混合 QM/MM 分子动力学模拟：OH− + CH3Cl → CH3OH + Cl−
DOI：
10.1002/jcc.10134
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发表时间：
2003
影响因子：
3
通讯作者：
T. Nitta
中科院分区：
文献类型：
--
作者：
Takumi Hori;Hideaki Takahashi;T. Nitta
采用混合真实的空间量子力学/分子力学（RS-QM/MM）方法研究了水溶液中离子型SN 2反应（OH− + CH 3Cl → CH 3OH + Cl−）的动力学溶剂化效应.已经证明，OH−接近甲基的过程被周围水（AW）中的水分子阻止，而反应在气相中容易发生。在SCW中观察到几乎相同的对OH−动力学的溶剂化效应，尽管水的体积密度与AW相比大幅降低。已经表明，由于OH-和水分子之间的强离子偶极相互作用，OH阴离子周围的SCW的溶剂化与AW的溶剂化局部相同。在过渡态，QM/MM模拟表明，过剩电子是相当灵活的，和电荷体积，以及原子上的分数电荷，严重依赖于瞬时溶剂配置。然而，它已被发现，在SCW中的溶剂化能可以定性地与系统的HOMO体积的玻恩方程。© 2002 Wiley Periodicals，Inc. J Comput Chem 24：209-221，2003
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. © 2002 Wiley Periodicals, Inc. J Comput Chem 24: 209–221, 2003