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首页> 外文期刊>Chemistry: A European journal >The Mates of S_N2 Reactions and Their Relation to Molecular and Solvent Properties
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The Mates of S_N2 Reactions and Their Relation to Molecular and Solvent Properties

机译：S_N2反应的产物及其与分子和溶剂性质的关系

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The energy barriers of symmetrical methyl exchanges in the gas phase have been calculated with the reaction path of the intersecting/interacting-state model (ISM). Reactive bond lengths increase down a column of the Periodic Table and compensate for the decrease in the force constants, which explains the near constancy of the intrinsic barriers in the following series of nucleophiles: F~- ≈ Cl~(-) ≈ Br~- ≈ I~-. This compensation is absent along the rows of the Periodic Table and the trend in the reactivity is dominated by the increase in the electrophilicity index of the nucleophile in the series C < N < O < F. Solvent effects have been quantitatively incorporated into the ISM model through a correlation between electrophilicity and the solvent acceptor number. This correlation is transferable between nucleophiles and solvents and allows the methyl transfer rate constants in solution to be calculated with remarkable simplicity and accuracy. The relationship between the S_N2 and electron-transfer mechanisms is clarified and it is shown that smaller solvent static effects should be expected for electron transfer in the absence of a thermodynamic driving force.
机译：利用相交/相互作用状态模型（ISM）的反应路径，计算了气相中对称甲基交换的能垒。反应性键长度在元素周期表的下一列增加并补偿力常数的减小，这解释了以下亲核试剂系列中本征势垒的近恒定性：F〜-≈Cl〜（-）≈Br〜- ≈我〜-在元素周期表的行中没有这种补偿，并且反应性的趋势主要由系列C

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