Theoretical Studies On The Radical-Molecule Reaction Mechanisms And Rate Constants Of Several Important Reactions

The quantum chemistry methods were used to investigate the singlet and triplet reaction mechanisms of NH (X3Σ-) + HCNO reaction. And using ab initio and density functional theory direct dynamics method to investigate the mechanism and rate constant of CN with chlorinated methanes CH4-nCln(n=1,2). These reactions are described as: NH(X3Σ-) + HCNO→products CN + CH3Cl→HCN + CH2Cl CN + CH2Cl2→HCN + CHCl2The results of this work show that:1. The theoretical study on the singlet and triplet potential energy surfaces of NH (X3Σ-) + HCNO reaction are investigated using DFT (UB3LYP) and BMC-CCSD methods with 6-311++G** basis set. The geometries, vibrational frequencies and the singlet point energy of all stationary points on potential energy surface (PES) are obtained. The results show that the title reaction is more favorable through the singlet potential energy surface than the triplet one. Moreover, both the singlet and triplet reactions of NH (X3Σ-) + HCNO have two attacking forms, which are N atom of NH (X3Σ-) attacking C atom or N atom of HCNO. The most stable product is P1 (HCN+HNO), this is accommodate with experiment.2. The theoretical study on the H-abstraction reaction mechanism and variational rate constant of the reaction CN + CH4-nCln(n=1,2) are investigated at UMP2 and UCCSD(T) levels with 6-311++G** basis set. The rate constants for the H-abstraction reaction of CN + CH4-nCln(n=1,2) are calculated by the classical transition state theory and canonical variational transition state theory (CVT) with small-curvature tunneling (SCT) correction in the temperature range 220-2000K. The results are consistant with experiment.