Theoretical study of the reaction of CH₂XO (X = F, Cl, Br) radicals with the NO radical

In this paper, we focus on the multiple-channel reactions of CH ₂XO (X = F, Cl, Br) radicals with the NO radical by means of direct dynamic methods. All structures of the stationary points were obtained at the MP2/6-311+G(d,p) level and vibrational frequency analysis was also performed at this level of theory. The minimum energy path (MEP) was obtained via the intrinsic reaction coordinate (IRC) theory at the MP2/6-311+G(d,p) level, and higher-level energetic information was refined by the MC-QCISD method. The rate constants for the three hydrogen abstraction reaction channels over the temperature range 200-1,500 K were calculated by the improved canonical variational transition state theory (ICVT) with a correction for small-curvature tunneling (SCT). The rate constants calculated in this manner were in good agreement with the available experimental data, and the three-parameter rate-temperature formulae for the temperature range 200-1,500 K were k _1a (T)=0.32× 10^-18T^1.83 exp (1748.54/T), k_2a(T)=0.22× 10^-19T^2.19 exp (1770.19/T), k_3a(T)=0.88× 10^-20T^2.20exp(1513.82/T) (in units of cm³ molecule^-1 s^-1).