Ab initio study on reaction path and rate constant of the hydrogen atom abstraction reaction HNCO+N→NCO+NH

Abstract

The reaction HNCO+N→NCO+NH has been studied using ab initio molecular orbital theory. The geometries of the reactant, complex, transition state, and products have been optimized at the UMP2/6-311G** level of theory. The forward and reverse reaction potential barriers were calculated accurately at the UMP4/6-311G** and UQCISD(T)/6-311G** levels of theory at the UMP2/6-311G** optimized geometries. The minimum energy path was calculated by the intrinsic reaction coordinate (IRC) theory at the UMP2/6-311G** level with a gradient step size of 0.05 (amu) 1/2 bohr. The changes of the geometries and normal mode vibrational frequencies along IRC were discussed. The MEP profile was refined by the UQCISD(T)/6-311G** level. The forward and the reverse reaction rate constants for the temperature range 1000–3000 K were obtained by the conventional and variational transition state theory. The theoretical rate constants of the forward reaction at the UQCISD(T) level are in good agreement with the rough estimate rate constants.