The mechanism of the reaction H+HNCO→NH2+CO that the first step producing an intermediate H2NCO complex is a controlling step has been calculated by ab initio MO method. On this basis, the reaction path, the dynamical properties along the reaction path and CVT (canonical variational theory) rate constants of the controlling step were investigated. The reults show that the recrossing and tunneling effects exist and the corrections by means of CVT method and small curvature approximation method are efficient respectively.

Key words: AMINES, REACTION MECHANISM, CARBON MONOXIDE, HYDROGEN, AB INITIO CALCULATION, REACTION RATE CONSTANT, ISOCYANIC ACID, TRANSITION STATE