论文部分内容阅读
采用密度泛函理论(DFT)方法在B3LYP/6-311G(d,p)水平上研究了硅苯和锗苯与2,3-二甲基丁二烯的两类杂Diels-Alder反应的微观机理、势能剖面、取代基效应和溶剂效应.计算结果表明,所研究反应均以协同非同步的方式进行,且C—Si或C—Ge键总是先于C—C键形成.在硅苯或锗苯分子作为杂亲二烯体的[2+4]反应中,endo进攻方式的非同步性比exo进攻稍大一些,而后者比前者一般要稍稍有利一些.在硅苯或锗苯分子作为杂二烯烃的[4+2]反应中,反应非同步性的大小与产物中不对称的亲二烯体上的取代基与硅或锗原子之间的相对位置有关,且在动力学上总是非同步性较大的反应更容易进行一些.硅或锗原子上的CCl3或NH2取代基在热力学和动力学上一般有利于反应的进行,而C(CH3)3取代基的影响则相反.[2+4]反应在热力学和动力学上均远比相应的[4+2]反应容易进行,这与实验完全一致.苯和甲醇溶剂对所研究反应的势能剖面影响较小.
The two kinds of hetero-Diels-Alder reactions of silica and germanium benzene with 2,3-dimethylbutadiene were investigated at the B3LYP / 6-311G (d, p) level using density functional theory (DFT) Mechanism, potential energy profile, substituent effect and solvent effect. The calculated results show that the studied reactions are carried out in a coordinated and asynchronous manner, and the C-Si or C-Ge bond always precedes the C-C bond. Or germanium molecules as heterodin [2 + 4] reaction, endo offensive attack is slightly more asynchronous than exo attack, and the latter is generally slightly more favorable than the former. In silico or germanium benzene molecules In the [4 + 2] reaction as a heterodiene, the magnitude of the reaction non-synchronism is related to the relative position of the asymmetric diaddune in the product to the silicon or germanium atom and is kinetically Reactions that are always more unsynchronized are easier to carry out.CCl3 or NH2 substituents on silicon or germanium atoms are generally thermodynamically and kinematically favored for the reaction, whereas C (CH3) 3 substituents have the opposite effect. The reaction of [2 + 4] was far more thermodynamically and kinetically easier than the corresponding [4 + 2] reaction, which was in good agreement with the experiment. Benzene and methanol The solvent has little effect on the potential energy profile of the studied reaction.