Abstract:The mechanisms of the reactions of CH (x211) with NH,, H,O, and H F have been studied by means of ab initio molecular orbital calculations incorporating electron correlation with Mdler-Plesset perturbation theory up to the second order. For each of the three CH reactions, the insertion path has been found in the potential energy surface; in the calculated insertion path there exists an intermediate complex prior to the transition state that has a lower energy than the reactants. Energetic results indicate that insertion paths are favourable channels for these CH reactions, which is in line with proposals based on kinetic experiments.Key words: CH radical, ammonia, water, hydrogen fluoride, reaction mechanism.

ZHONGHUA Yu, CONGXIANG CHEN, and MINGBAO HUANG. Can. J. Chem. 71, 512 (1993).The mechanism of the reaction CH(X'T) + CH, has been investigated by ab initio molecular orbital calculations.Addition, insertion, and abstraction-addition reaction paths have been examined by, in total, five methods of approach. The addition reaction path has a rather high energy barrier. Our calculations have implied that the assumed insertion reaction path does not seem to exist for the reaction CH + CH,, and a two-step mechanism (abstraction-addition reaction path) was then proposed. For the abstraction-addition reaction, the reactants, transition state, intermediates, and products were optimized at the HF/3-21G and HF/6-31G" levels, and vibrational frequencies were calculated at the HF/3-21G level. Electronic correlation energy was estimated by means of the M~ller-Plesset perturbation theory and configuration interaction method. The excited-state abstraction reaction was also studied in some detail.