Theoretical study of the mechanisms and rate constants on the reaction of H2CNH with O(3P)

The multiple-pathway reaction system of H2CNH and O(3P) has been investigated by ab initio methods. The optimized geometries and frequencies of all stationary points as well as the minimum energy paths (MEPs) are computed at the QCISD/cc-pVDZ level. The single point energies of the stationary points are refined at the QCISD(T)/aug-cc-pVTZ level. The rate constants of two H-abstraction pathways, H2CNH + O → H2CN + OH and H2CNH + O → HCNH + OH, are evaluated by conventional transition state theory (TST) and improved canonical variational transition state theory (ICVT) methods at the temperature range from 200 to 2500 K. Small-curvature tunneling (SCT) effect is taken into consideration. The computational results show that the variational effect for reaction H2CNH + O → H2CN + OH is larger than that for reaction H2CNH + O → HCNH + OH. In the lower temperature range, the SCT effect is important for the H-abstractions. Theoretical rate constants are generally close to experimental data. The ICVT/SCT theoretical rate constants are expressed in three-parameter formula as k = 1.64 × 10−17 T1.81 exp (−962.61/T) cm3 molecule−1 s−1 for the former pathway and k = 2.98 × 10−19 T2.43 exp (−692.65/T) cm3 molecule−1 s−1 for the latter pathway.