RN (R＝CH3, CH3CH2)异构化及脱氢反应的量子拓扑研究

利用量子化学从头算CASSCF方法在6-311＋G (d, p)基组水平上对单线态和三线态RN (R＝CH₃, CH₃CH₂)异构化反应及RN脱氢反应的微观机理进行了理论研究. 在MP2/6-311＋G (d, p)和CCSD/6-311＋G (d, p)水平上进行了单点能校正. 单态和三态势能面的交叉点(ISC)的存在清楚地说明了基态反应物³RN异构化为基态产物¹R'NH (R'＝CH₂, CH₃CH)的过程. 电子密度拓扑分析显示在整个异构化过程中有两种类型的结构过渡态: 单态反应通道为T型过渡态, 三态反应通道为环状过渡态. 单线态RN脱氢反应通道中“原子-分子键”的存在说明两个H原子是以H₂的形式从RN中脱去的.

Quantum Topological Studies on the Isomerization and H2 Elimination Reaction of RN (R=CH3, CH3CH2)

The isomerization reactions of singlet state and triplet state RN (R＝CH₃, CH₃CH₂)→R'NH (R'＝CH₂, CH₃CH), and hydrogen elimination reactions of RN have been investigated at CASSCF/6-311＋G (d, p) level. The single point energies are obtained at MP2/6-311＋G (d, p) and CCSD/6-311＋G (d, p) levels. The intersystem crossing (ISC) of the singlet and triplet potential surface during the RN (R＝CH₃, CH₃CH₂) isomerization illustrates clearly how the ground-state reactants ³RN (R＝CH₃, CH₃CH₂) transform to ground-state products ¹R'NH (R'＝CH₂, CH₃CH). The topological analysis of electron density shows that there exist two kind of structure transitional structure (STS) in the whole isomerization: a T-shaped conflict STS appears in the singlet isomeration channel and a bifurcation-type ring structure appears in the triplet isomeration channel. The “atom-molecule bond”, which exists in the H₂ elimination channel, shows that two hydrogen atoms eliminate from CH₃N as a H₂ molecule.