A DFT and ab initio study on the mechanisms of atmospheric CH2NH + O(3P) reaction

The mechanisms for the reaction of CH2NH with atomic oxygen on the triplet PES were studied in details using ab initio and DFT methods. All stationary points involved in the title reaction were optimized at the B3LYP, PW1PW91 and MP2 methods conjunct with the 6-311++G(d,p) and aug-cc-pVDZ basis set, and more accurate energies were calculated with the G4 method. The results reveal that the addition/elimination and direct hydrogen abstraction mechanisms were determined, and the former one is more feasible. The most favorable channel involves the association of CH2NH with O atom to form OCH2NH (IM1) via a low barrier, which converses to another OCH3NH (IM1′) by internal rotation, and finally the NC bond dissociates to give out CH2O + NH via another low barrier. The direct hydrogen abstraction channels are less favorable compared with the addition/elimination channel stated above. However, they are of some important at high temperature condition such as combustion. For completeness, the mechanisms on the singlet PES was revealed as well.