Mechanism of Nucleophilic Aromatic Substitution of 1-Chloro-2,4-dinitrobenzene by Glutathione in the Gas Phase and in Solution. Implications for the Mode of Action of Glutathione S-Transferases
Mechanism of Nucleophilic Aromatic Substitution of 1-Chloro-2,4-dinitrobenzene by Glutathione in the Gas Phase and in Solution. Implications for the Mode of Action of Glutathione S-Transferases
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DOI：
10.1021/ja963177v
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发表时间：
1997-01
影响因子：
15
通讯作者：
Ya-Jun Zheng;R. Ornstein
中科院分区：
文献类型：
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作者：
Ya-Jun Zheng;R. Ornstein
利用从头算分子轨道理论结合连续溶剂模型，在 HF/6-31G*、HF/6-31+G** 和 MP2/6-31+G** 理论水平上阐明了谷胱甘肽（以甲硫醇离子为模型）在气相和溶液中亲核芳香取代 1-氯-2,4-二硝基苯的反应机理。两种离子-分子配合物在HF水平处位于气相中，但只有一种在MP2/6-31+G**水平处存在，而在水溶液中都不存在。在水溶液中，存在较大的自由能垒，C−S键的形成是速率决定步骤，这与实验观察结果一致。计算出的HF/6-31+G**理论水平的自由能垒（30.2 kcal/mol）似乎与实验（23.8 kcal/mol）吻合较好，而MP2/6-31+G**势垒太低，表明MP2/6-31+G**理论水平可能高估了C−S键形成过渡态的稳定性。对模式的影响...
The reaction mechanism of nucleophilic aromatic substitution of 1-chloro-2,4-dinitrobenzene by glutathione (as modeled by a thiomethoxide ion) in the gas phase and in solution was elucidated using ab initio molecular orbital theory in combination with a continuum solvent model at the HF/6-31G*, HF/6-31+G**, and MP2/6-31+G** levels of theory. Two ion−molecule complexes were located in the gas phase at the HF level, but only one exits at the MP2/6-31+G** level, while neither exits in aqueous solution. In aqueous solution, there is a large free energy barrier and C−S bond formation is the rate-determining step, which is in agreement with experimental observation. The calculated free energy barrier (30.2 kcal/mol) at the HF/6-31+G** level of theory seems to be in good agreement with experiment (23.8 kcal/mol), while the MP2/6-31+G** barrier is too low, indicating that the MP2/6-31+G** level of theory probably overestimates the stability of the transition state for C−S bond formation. Implications for the mode...