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首页> 美国卫生研究院文献>Proceedings of the National Academy of Sciences of the United States of America >Nonenzymatic and enzymatic hydrolysis of alkyl halides: A theoretical study of the SN2 reactions of acetate and hydroxide ions with alkyl chlorides
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Nonenzymatic and enzymatic hydrolysis of alkyl halides: A theoretical study of the SN2 reactions of acetate and hydroxide ions with alkyl chlorides

机译：烷基卤的非酶水解和酶水解： 乙酸和乙酸的SN2反应的理论研究。 烷基氯化物产生氢氧根离子

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摘要

The SN2 displacements of chloride ion from CH3Cl, C2H5Cl, and C2H4Cl2 by acetate and hydroxide ions have been investigated, using ab initio molecular orbital theory at the HF/6–31+G(d), MP2/6–31+G(d), and MP4/6–31+G(d) levels of theory. The central barriers (calculated from the initial ion–molecule complex) of the reactions, the differences of the overall reaction energies, and the geometries of the transition states are compared. Essential stereochemical changes before and after the displacement reactions are described for selected cases. The gas phase reactions of hydroxide with CH3Cl, C2H5Cl, and C2H4Cl2 have no overall barrier, but there is a small overall barrier for the reactions of acetate with CH3Cl, C2H5Cl, and C2H4Cl2. A self-consistent reaction field solvation model was used to examine the SN2 reactions between methyl chloride and hydroxide ion and between 1,2-dichloroethane and acetate in solution. As expected, the reactions in polar solvent have a large barrier. However, the transition state structures determined by ab initio calculations change only slightly in the presence of a highly polar solvent as compared with the gas phase. We also calibrated the PM3 method for future study of an enzymatic SN2 displacement of halogen.
机译：利用从头算分子轨道理论，在HF / 6–31 + G（d），MP2 / 6–31 + G（d）上研究了乙酸根和氢氧根离子对氯离子从CH3Cl，C2H5Cl和C2H4Cl2的SN2置换）和MP4 / 6–31 + G（d）的理论水平。比较了反应的中心势垒（从初始离子-分子络合物计算），总反应能的差异以及过渡态的几何形状。描述了所选情况下置换反应前后的基本立体化学变化。氢氧化物与CH3Cl，C2H5Cl和C2H4Cl2的气相反应没有总阻隔，但是乙酸盐与CH3Cl，C2H5Cl和C 2 H 4的反应的总阻隔很小 Cl 2 。使用自洽反应场溶剂化模型检查S N 2反应 介于氯甲烷和氢氧根离子之间 溶液中有1,2-二氯乙烷和乙酸盐。不出所料 在极性溶剂中有较大的阻隔作用。但是，过渡状态 从头算计算确定的结构发生变化 与高极性溶剂相比，只有一点点 与气相。我们还校准了PM3方法以备将来研究 酶S N 2取代卤素的机理

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