雷酸与甲醇加成反应机理的量化研究

QUANTUM CHEMICAL STUDIES ON ADDITIVE REACTION OF FULMINIC ACID WITH METHANOL

本文用 SCF MO ab initio法研究了甲醇与雷酸的亲核加成反应。所有计算采用 STO-3G基组。反应物、产物及过渡态的结构均进行了全优化。过渡态的结构通过其力常数矩阵有唯一负本征值而得到确证。雷酸在甲醇分子的诱导下易发生E式变型。这种变型决定了反应的立体化学性质,使五员环状氢键活化络合物得以形成,质子从甲醇氧转移到雷酸氧原子上发生在过渡态形成之时或之后。这种质子转移不需活化能,两个氧原子的适宜取向及电荷的转移促进了质子的“滑动”。整个反应为一步进行的放热反应。

The five-centred H-bond complex of fulminic acid with methanol as a nucleophile has been studied using ab initio method with STO-3G basis set. SCF calculations were performed with complete geometry optimizations.The structure of the TS was verified by the criterion-the Hessian matrix has one, and only one, negative eigenvalue. Fulminic acid is most easily bent in the E direction and this is the configuration induced in the stereospecific nature of the reaction. The transfer of a proton from the oxygen of the attacking methanol to that of the fulminic acid occurs at or just after the TS with no energy barrier. The stereospecif-icity of the two oxygen atoms which are correctly oriented and the charge transfer faciliate the 'proton slide'. The reaction is exothermic and proceeds in one step.