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Mechanism of organic reaction in solution : kinetics experiment and new QM/MM computations

溶液中有机反应机理：动力学实验和新的QM/MM计算

基本信息

批准号：
15550034
负责人：
YAMATAKA Hiroshi
金额：
$ 2.43万
依托单位：
Rikkyo University (2004)Osaka University (2003)
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2003
资助国家：
日本
起止时间：
2003 至 2004
项目状态：
已结题

项目摘要

Computational study with a QM/MM method has been carried out for S_N1-S_N2 reactions of alkyl halides in water, and the effect of solvent on the reaction pathways and the transition state structures was analyzed. The results were presented in domestic and oversea meetings. We are currently studying organic reactions in solution with Fragment MO(FMO) method as well.Activation and reaction energies were calculated for acid-base reactions of nitromethane, nitroethane, and substituted phenyllnitromethanes in the gas phase, water-solvated cluster, and solution systems. The experimentally observed nitroalkane anomaly in the proton-transfer rate-equilibrium correlation for the nitromethane and nitroethane systems was reproduced in solution but not in the gas phase. The origin of the anomaly was analyzed, and the importance of solvation was demonstrated. However, the anomaly in the Bronsted correlation for the arylnitromethane system could not be reproduced computationally even in solution. We plan to elucidate this problem by using QM/MM and FMO methods.Kinetic study was carried out for the carbonyl addition reactions. Stopped-flow experiment for the reactions of substituted benzaldehyde and benzopohenones with RLi and RMgX revealed that these reagents exist as aggregates (tetramer or dimer) and react as monomers. Other basic organic reactions such as molecular rearrangements and keto-enol isomerizations were studied both experimentally and computationally.

采用QM/MM方法对烷基卤化物在水中的S_N1-S_N2反应进行了计算研究，分析了溶剂对反应路径和过渡态结构的影响。研究结果已在国内外会议上发表。我们目前也在用片段MO（Fragment MO， FMO）方法研究溶液中的有机反应。计算了硝基甲烷、硝基乙烷和取代苯基亚硝基甲烷在气相、水溶剂团簇和溶液体系中酸碱反应的活化能和反应能。在硝基甲烷和硝基乙烷体系的质子转移速率平衡相关中，实验观察到的硝基烷烃异常在溶液中重现，但在气相中没有重现。分析了异常的成因，论证了溶化作用的重要性。然而，芳基硝基甲烷体系的Bronsted相关异常即使在溶液中也不能计算重现。我们计划通过QM/MM和FMO方法来阐明这个问题。对羰基加成反应进行了动力学研究。对取代苯甲醛和苯甲酮与RLi和RMgX反应的停流实验表明，这些试剂以聚集体（四聚体或二聚体）的形式存在，并以单体形式反应。其他基本的有机反应，如分子重排和酮烯醇异构化进行了实验和计算研究。