Electronic Structure Theory Study of the Microsolvated F-(H2O) + CH3I S(N)2 Reaction
Electronic Structure Theory Study of the Microsolvated F-(H2O) + CH3I S(N)2 Reaction
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微溶剂化F-(H2O)CH3I S(N)2反应的电子结构理论研究
DOI：
10.1021/acs.jpca.6b00726
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发表时间：
2016
影响因子：
2.9
通讯作者：
Sheng Li
中科院分区：
文献类型：
--
作者：
Zhang Jiaxu;Yang Li;Sheng Li
通过大量的电子结构计算，对微水合氟离子与甲基碘反应的势能分布进行了表征。在反应入口处形成了氢键F-（H_2O）-HCH_2 I和离子偶极F-（H_2O）-CH_3 I复合物，并且在这些复合物附近的PES非常平坦，这可能对反应动力学具有重要意义。水分子保持在氟侧，直到反应体系到达SN 2鞍点。它可以很容易地移动到碘侧，几乎没有障碍，但在一个非同步的反应路径后的动力学瓶颈的反应，这支持了以前的预测微溶剂化的SN 2系统。通过与非溶剂化的类似物和其它微溶剂化的SN 2体系的比较，探讨了溶剂化水分子对反应机理的影响。以基于MP2优化几何构型的CCSD（T）单点计算为基准，发现DFT泛函B 97 -1和B3 LYP能更好地表征标题反应的势能分布，并推荐为揭示动力学行为的直接动力学模拟的首选方法.
The potential energy profile of microhydrated fluorine ion reaction with methyl iodine has been characterized by extensive electronic structure calculations. Both hydrogen-bonded F–(H2O)---HCH2I and ion–dipole F–(H2O)---CH3I complexes are formed for the reaction entrance and the PES in vicinity of these complexes is very flat, which may have important implications for the reaction dynamics. The water molecule remains on the fluorine side until the reactive system goes to the SN2 saddle point. It can easily move to the iodine side with little barrier, but in a nonsynchronous reaction path after the dynamical bottleneck to the reaction, which supports the previous prediction for microsolvated SN2 systems. The influence of solvating water molecule on the reaction mechanism is probed by comparing with the influence of the nonsolvated analogue and other microsolvated SN2 systems. Taking the CCSD(T) single-point calculations based on MP2-optimized geometries as benchmark, the DFT functionals B97-1 and B3LYP are found to better characterize the potential energy profile for the title reaction and are recommended as the preferred methods for the direct dynamics simulations to uncover the dynamic behaviors.