硫代草酸异构体结构及异构化反应机理的理论研究

Theoretical Study on the Structures and Isomerization of HO(S)CC(S)OH

采用量子化学CBS-QB3组合方法对硫代草酸可能存在的异构体构型及异构体间相互转化机理进行了详细计算研究,分别得到11种稳定结构及12种异构化过渡态。其中硫代草酸异构体的相对稳定性顺序为M11>M7>M10>M1>M9>M6>M2>M3=M4>M5,不稳定异构体M5极易向稳定异构体转化。异构体M6向M11转化仅需越过1.92k J·mol-1的能垒,且放出49.04k J·mol-1能量,因此M6向M11的转化是H迁移异构化反应的主通道。

The stability and isomerization mechanisms of HO （S）CC （S）OH have been investigated by the CBS- QB3 composite approach. Eleven isomers and twelve transition states were obtained and the possible reaction pathways were probed. The results indicated that the order of stability is M11 〉 M7 〉 MIO 〉 M1 〉 M9 〉 M6 〉 M2 〉 M3 = M4 〉 M5. The activation free energy associated with the C-C bond rotation paths are all small, and they are easily converted into the O-H bond rotation isomers. In addition, the isomerization of M6 to Mll is most favorable both thermodynamically and kinetically in all isomerizations, which should be the dominant process.