The mechanisms of N-Arylideneaminoamides’ gas-phase pyrolytic decomposition with the production of benzene nitrile and benzamide are studied by density function theory.The geometries of the reactant, transition states, intermediates and products are optimized at the B3LYP/6-31G(d,p) level. Vibration analysis is carried out to confirm its identity as transitions structure, the intrinsic reaction coordinate(IRC) is performed to search the minimum energy path. Three possible reaction channels are shown, including the one concerted reaction of direct pyrolytic decomposition and the two of first becoming ring-like compound then concerted reaction of direct pyrolytic decomposition. The concerted reaction of direct pyrolytic decomposition has the lower activation barrier of all the three channels and therefore it occurs more often than the others

Key words: density functional theory, N'-benzylidene-benzohydrazide, reaction mechanism