Reactions of carbynes. Potential energy surfaces for the doublet and quartet methylidyne (CH) reactions with molecular hydrogen

Abstract

The CH(2Π)+H2→CH3 and CH(4Σ−)+H2→CH2(3B1)+H reactions have been studied using ab initio molecular electronic structure theory. Basis sets used were of double zeta (DZ) quality and DZ augmented by polarization functions. For the insertion reaction, the least motion barrier height is quite high, ∼75 kcal/mole. However, nonleast motion pathways are much more favorable, involving little or no barrier. In both respects this potential energy surface is analogous to that for the methylene insertion CH2(1A1)+H2→CH4. The quartet abstraction has a sizeable barrier, ∼11 kcal, associated with it, in analogy with the triplet methylene abstraction CH2(3B1)+H2→CH3+H.