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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >A Density Functional Study of the Acetoxylation of Ethylene to Vinyl Acetate Catalyzed by Palladium Acetate
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A Density Functional Study of the Acetoxylation of Ethylene to Vinyl Acetate Catalyzed by Palladium Acetate

机译：乙酸钯催化乙烯乙酰氧基化为乙酸乙烯酯的密度泛函研究

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摘要

Vinyl acetate can be formed in the homogeneous reaction of ethylene with palladium acetate in glacial acetic acid. We propose a Wacker-like mechanism, which has been studied using density functional theory computational methods. The palladium acetate dimer, which is presumably the active catalyst, has been modeled by clusters of two palladium ions coordinated by acetate ligands. The active site is formed by a single palladium ion which is part of the dimer. in this mechanism, ethylene coordinates to palladium by substitution of a terminal acetate. Next, the ligand couples with an acetate ion, and consecutive #beta#-hydrogen transfer forms the product vinyl acetate. The coupling probably takes place via an outer sphere attack by acetate. Theory suggests that the rate-determining step is the #beta#-hydrogen transfer, and the activation energy is predicted to be 67 kJ/mol. Molecules from the solvent act as a catalyst in this step. However, at high acetate concentration, formation of a vacancy at a terminal acetate site is inhibited, which results in a negative reaction order with respect to acetate. Solvent effects are explicitly taken into account in all steps as a correction to the energies obtained in a vacuum.
机译：乙酸乙烯酯可以在乙烯与乙酸钯在冰醋酸中的均相反应中形成。我们提出了一种类似于Wacker的机制，该机制已使用密度泛函理论计算方法进行了研究。醋酸钯二聚体（大概是活性催化剂）已通过醋酸钯配体配位的两个钯离子簇进行建模。活性位点由作为二聚体一部分的单个钯离子形成。在这种机理下，乙烯通过取代末端乙酸酯配位为钯。接下来，配体与乙酸根离子偶合，并且连续的＃beta＃-氢转移形成产物乙酸乙烯酯。耦合可能是通过醋酸盐对外球的侵蚀而发生的。理论表明，决定速率的步骤是＃beta＃-氢转移，活化能预计为67 kJ / mol。来自溶剂的分子在该步骤中充当催化剂。然而，在高乙酸盐浓度下，在乙酸盐末端位点的空位形成受到抑制，这导致相对于乙酸盐的反应顺序为负。在所有步骤中都明确考虑了溶剂效应，作为对在真空中获得的能量的校正。

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