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采用密度泛函理论(DFT)方法在B3LYP/6-311G(d,p)水平上研究了硅杂苯与甲醛和二苯甲酮的Diels-Alder反应的微观机理、势能剖面和取代基效应.计算结果表明,所研究反应均为协同的基元反应,形成1个Si-O键的反应中2个新键的形成具有较大的非同步性,而其他反应的非同步性相对较小.羰基碳原子上的苯基取代基不利于反应的进行,而硅杂苯分子中硅原子上的C(CH3)3与CCl3取代基有利于反应的进行.硅原子参与的反应在热力学和动力学上均远比不涉及硅原子的反应容易进行,而形成1个Si-O键的反应比形成1个Si-C键的反应容易进行,此结果与实验一致.
The micro-mechanism, potential energy profile and substituent effect of Diels-Alder reaction of silabenzene with formaldehyde and benzophenone were studied by density functional theory (DFT) at B3LYP / 6-311G (d, p) The calculated results show that all the reactions studied are coordinated elementary reactions. The formation of two new bonds in the reaction of forming one Si-O bond has a great asymmetry, while the other reactions have a relatively small non-synchronization. The phenyl substituent on the carbonyl carbon atom is unfavorable to the reaction, while the C (CH3) 3 and CCl3 substituents on the silicon atom in the silabenzene molecule are favorable for the reaction. The reactions involving the silicon atom in the thermodynamics and kinetics Is far easier than the reaction involving no silicon atom, and the reaction for forming one Si-O bond is easier to perform than the reaction for forming one Si-C bond. This result is in agreement with the experiment.