摘要
本文用ab initio RHF/4-31G基组研究了甲醇1,1脱氢反应的微观反应动力学,用能量梯度法优化出反应物、过渡态和产物的几何,计算了反应热、活化能、频率因子和在500K时的活化熵.用内禀反应坐标(IRC)方法进行了反应路径解析,并且对反应物、过渡态和反应路径进行了正则振动分析,做出了反应的振动频率相关图。
The 1, 1 dehydrogenation reaction of methanol was investigated by ab initio MO calculations using RHF/4-31G basis set. The energy gradient method was used to optimize the equilibrium geometries of the reactant, the transition state and the product. The activation energy and reaction heat were calculated to be 454.2 kJ·mol^(-1) and 365.2kJ·mol^(-1), respectively. The results indicate that the 1, 1 dehydrogenation path of methanol is favourable to occur than the 1, 2 path in terms of activation energy and entropy factors but unfavourable in terms of reaction heat. The reaction ergodography was analyzed by means of intrinsic reaction coordinate (IRC) method. The changes .of some physical properties along IRC were followed and the results indicate that the stretching of the two CH bonds are not in step with each other in the process of the 1,1 dehydrogenation reaction. The vibrational analyses of the reactant, transition state and the reaction coordinate were carried out by the nu(?)erial differentiation method and the vibrational frequency correlation diagram was made and found that the CO and OH stretching vibrations are adiabatic while the symmtical stretching vibration of CH bonds which are approximately in the direction of the IRC at the early stage of the reaction are important to themode selectivity of the 1,1 dehydrogenation reaction of methanol.
