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通过密度泛函理论计算,研究锰氧咔咯催化环己烷氧化成己二醛的反应,讨论该催化过程的多态反应活性.计算表明,该反应经历两步羟基化和一步C—C键断裂过程.两步羟基化都是由氢转移开始,形成碳自由基中间体,接着迅速发生的自由基反应形成二醇的中间体.C—C键断裂过程由氢转移开始,先形成氧自由基中间体,氧自由基单电子和邻近环C—C键存在强烈的相互作用,导致该C—C键活化断裂和第二个氢的协同转移.反应的速控步是第二步羟基化过程,因此碳自由基中间体的稳定性决定该反应的难易,这也解释了实验上观察到叔碳的活性大于仲碳的活性顺序.
The density functional theory (DFT) calculations were used to study the oxidation of cyclohexane to hexanedicarboxylate catalyzed by manganese oxycarbazole.The polymorphism of the catalytic reaction was discussed.The calculated results showed that the reaction proceeded through two steps of hydroxylation and one-step C-C bond Breaking process. Two-step hydroxylation is initiated by hydrogen transfer, the formation of carbon radical intermediates, followed by rapid radical reaction to form diol intermediates. C-C bond cleavage process from hydrogen transfer, the first form of oxygen free Base intermediate, oxygen radical single electron and the adjacent ring C-C bond there is a strong interaction, resulting in the C-C bond activation fracture and the second hydrogen co-transfer reaction speed control step is the second hydroxylation Therefore, the stability of the carbon radical intermediate determines the difficulty of the reaction, which also explains the experimentally observed activity of tertiary carbon greater than that of secondary carbon.