High level ab initio calculations have been performed to study the mechanism and kinetics of the reaction of the cyanomethylene radical (HCCN) with the NO. The species involved have been optimized at the B3LYP/6-311++G(3df,2p) level and their corresponding single-point energies are improved by the CCSD(T)/aug-cc-PVQZ// B3LYP/6-311++G(3df,2p) approach. From the calculated potential energy surface, we have predicted that that the favorable pathways for the formation of several isomers of an HCCNNO complex.
Formations of HCN + NCO (P1) and HCNO + CN (P3) are also probable, although these two pathways require little thermal activation. To rationalize the scenario of our calculated results, we also employ the Fukui functions and HSAB theory to seek the possible clues.
The predicted total rate coefficient, ktotal, at He pressure 760 torr can be represented with an equation: ktotal = 1.40×10-7 T-2.01 exp(3.15 kcal mol-1/RT) at T = 298–3000 K, in units of cm3 molecule-1 s-1. The predicted total rate coefficients at some available conditions (18 and 30 torr) are in good agreement with experimental observation. In addition, the rate constants for key individual product channels are provided in different temperature and pressure conditions.
