The hydration mechanism of ketene: 15 years later
The hydration mechanism of ketene: 15 years later
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DOI：
10.1139/v99-090
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发表时间：
1999
影响因子：
1.1
通讯作者：
M. Nguyen;Greet Raspoet
中科院分区：
文献类型：
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作者：
M. Nguyen;Greet Raspoet
用理论方法对乙酸乙烯酮(H_2C=C=O+H_2O·→>；CH_3COOH)在气相和溶液中水合的详细机理有了新的认识。气相计算采用从头算分子轨道理论，体溶剂效应采用自洽反应场方法(SCRF)和极化连续介质模型(PCM)。通过含有两个、三个和四个水分子的水簇合物的攻击模拟的水化作用证实，如1984年首次证明的那样，将水两步加到烯酮C=O键上，产生1，1-亚二醇中间体，在能量上，略有但始终如一地优先于直接导致酸性产物的C=C键上的协同加成。试图在溶液中找到两性离子中间体，但没有成功。气相超系统中至少存在一个由三个氢键水分子组成的团簇，以促进质子转移。进一步合并法案..。
New insights into the detailed mechanism of the hydration of ketene yielding acetic acid (H2C=C=O + H2O →> CH3COOH) were obtained by theoretical methods in both gas phase and solution. While gas phase calculations were performed using ab initio molecular orbital theory, bulk solvent effects were included using the self-consistent reaction field method (SCRF) and the polarizable continuum model (PCM). The hydration modeled by attack of water clusters containing two, three, and four water molecules confirms that a two-step addition of water to the ketene C=O bond, yielding a 1,1-enediol intermediate as initially demonstrated in 1984, is energetically, slightly but consistently, preferred over a concerted addition across the C=C bond leading directly to the acid product. Attempts to locate a zwitterion intermediate in solution were not successful. At least a cluster of three hydrogen-bonded water molecules is present in the gas phase supersystem to facilitate the proton transfer. Further incorporation of act...