The ab initio calculations have been performed on the reaction paths of 1, 1- and 1, 2-dehydrogenation of methylamine by the Intrinsic Reaction Coordinate (IRC) method. The transition state structures and the potential energy curves have been determined, and the activation energies, reaction heats, the activation entropies, and reactional frequency factors have been obtained on the RHF/4-31G level. The mode- selective study reveals the IRC of 1, 1- and 1, 2-H~2 elimination to be connected respectively with the deformation modes of 1057 and 1438cm^-^1 of the reactant. The vibration coupling between the normal coordinates occured in either of these two reaction paths. These results have provided an useful information and theoretical introduction for the studying of laser-inducing and mode-selective chemical reactions.

Key words: DEHYDROGENATION REACTION, METHANAMINE, IRC, CHEMICAL REACTION, MICRO KINETICS, ACTIVATION ENERGY, POTENTIAL ENERGY, CALCULATION