A Theoretical Study of the CH2N System: Reactions in both Lowest Lying Doublet and Quartet States

Abstract

Ab initio molecular orbital calculations at the second-order perturbation theory (UMP2) and coupled cluster singles and doubles with corrected triples (CCSD(T)) levels with 6-311++G(d,p) and 6-311++G(3df,3dp) basis sets have been carried out to construct the potential energy surfaces related to the various reactions of the [CH2N] system, including H2+CN, H+HCN, and H+HNC in both lowest lying doublet and quartet electronic states. Barrier heights, vibrational wavenumbers, and moments of inertia were then utilized in the calculations of rate constants using a quantum Rice−Ramsperger−Kassel (QRRK) theory. The calculated total rate constant k∞ for the H+HCN reaction at 300 K is 2.2 × 107 cm3 mol-1 s-1 and is suggestive of a slow reaction and it corresponds predominantly to the stabilization of the adducts. On the other hand, the H+HNC reaction is calculated to be a pressure-independent fast reaction with a rate coefficient of 1.9 × 1011 cm3 mol-1 s-1 leading primarily to H+HCN dissociation products. The standard heat of formation of the H2CN radical is estimated to be Δ = 56 ± 3 kcal/mol (57 ± 3 kcal/mol at 0 K).