College of Physics and Electronics, Shandong Normal University, Jinan, China.
J Phys Chem A. 2012 Mar 8;116(9):2371-6. doi: 10.1021/jp3005986. Epub 2012 Feb 29.
The bimolecular nucleophilic substitution reaction of CCl(4) and OH(-) in aqueous solution was investigated on the basis of a combined quantum mechanical and molecular mechanics method. A multilayered representation approach is employed to achieve high accuracy results at the CCSD(T) level of theory. The potential of mean force calculations at the DFT level and CCSD(T) level of theory yield reaction barrier heights of 22.7 and 27.9 kcal/mol, respectively. Both the solvation effects and the solvent-induced polarization effect have significant contributions to the reaction energetics, for example, the solvation effect raises the saddle point by 10.6 kcal/mol. The calculated rate constant coefficient is 8.6 × 10(-28) cm(3) molecule(-1) s(-1) at the standard state condition, which is about 17 orders magnitude smaller than that in the gas phase. Among the four chloromethanes (CH(3)Cl, CH(2)Cl(2), CHCl(3), and CCl(4)), CCl(4) has the lowest free energy activation barrier for the reaction with OH(-) in aqueous solution, confirming the trend that substitution of Cl by H in chloromethanes diminishes the reactivity.
在量子力学和分子力学相结合的方法基础上，研究了四氯化碳（CCl(4)）和氢氧根（OH(-)）在水溶液中的双分子亲核取代反应。采用多层表示方法，在 CCSD(T)理论水平上实现了高精度的结果。在 DFT 水平和 CCSD(T)理论水平上的势能平均力计算得出的反应势垒高度分别为 22.7 和 27.9 kcal/mol。溶剂化效应和溶剂诱导极化效应对反应能学都有显著的贡献，例如，溶剂化效应使鞍点升高了 10.6 kcal/mol。在标准状态下，计算得到的速率常数系数为 8.6×10(-28) cm(3) molecule(-1) s(-1)，约比气相中的小 17 个数量级。在四种氯甲烷（CH(3)Cl、CH(2)Cl(2)、CHCl(3)和 CCl(4)）中，CCl(4)与 OH(-)在水溶液中的反应具有最低的自由能活化势垒，这证实了氯甲烷中氯被氢取代会降低反应活性的趋势。
