Theoretical Study on Reaction Mechanisms and Kinetics of Cyanomidyl Radical with NO

Abstract

The mechanisms and kinetics of the reaction of the cyanomidyl radical (HNCN) with the NO have been investigated by the high-level ab initio molecular orbital method in conjunction with VTST and RRKM theory. The species involved have been optimized at the B3LYP/6-311++G(3df,2p) level and their single-point energies are refined by the CCSD(T)/aug-cc-PVQZ//B3LYP/6-311++G(3df,2p) method. Our calculated results indicate that the favorable pathways for the formation of several isomers of an HNCN-NO complex. Formations of HNC + N(2)O (P1) and HNCO + N(2) (P2) are also possible, although these two pathways involve little activation energy. Employing the Fukui functions and HSAB theory, we are able to rationalize the scenario of the calculated outcome. The predicted total rate constants, k(total), at a 760 Torr Ar pressure can be represented by the equations k(total) = 4.39 x 10(8) T(-7.30) exp(-1.76 kcal mol(-1)/RT) at T = 298-1000 K and 1.01 x 10(-32) T(5.32) exp(11.27 kcal mol(-1)/RT) at T = 1050-3000 K, respectively, in units of cm(3) molecule(-1) s(-1). In addition, the rate constants for key individual product channels are provided in a table for different temperature and pressure conditions. These results are recommended for combustion modeling applications.