分子CH_3NH=B:的结构及重排反应的理论研究

采用量子化学中的从头计算方法, 在MP2/6-31G(d,p)水平上研究了不饱和硼烯CH3NH=B:的结构及重排反应机理。结果表明, CH3NH=B:的单线态结构比三线态结构稳定, 该分子的基态是单线态。分子CH3NH=B:可以发生3种不同的重排反应。本文找到了这3种重排反应的过渡态, 并详细计算了不饱和硼烯CH3NH=B:重排反应的动力学函数, 据此讨论了不饱和硼烯CH3NH=B:的稳定性问题。

Theoretical Studies on the Structure and Rearrangement Reactions of Singlet State of CH3NH=B:

The structures and mechanisms of rearrangement reactions of CH3NH=B: have been studied by using ab initio method of quantum chemistry at the MP2/6-31G(d,p) level. Computational results reveal that the energy of singlet state of CH3NH=B: is lower than that of the triplet state, so the ground state of CH3NH=B: is singlet. The mechanisms of three rearrangement reactions of singlet state of CH3NH=B: have been determined at the MP2/6-31G(d,p) level and three transition states have been gained. The mechanism of the first rearrangement reaction is the hydrogen atom linked to nitrogen atom transferring to boron atom, and that of the second and third ones is the methyl linked to nitrogen atom transferring to boron atom and the hydrogen atom of methyl transferring to boron atom, respectively. According to the results at MP2/6- 31G(d,p) level, the kinetic properties of three rearrangement reactions have been calculated. On basis of the activation free energy DG, the stability of singlet state of CH3NH=B: has been discussed. The stability of CH3NH=B: is similar to that of H2N=B:, but more stable than that of H2C=C:.