Theoretical study of the reaction of CH 2 XO (X = F, Cl, Br) radicals with the NO radical

In this paper, we focus on the multiple-channel reactions of CH 2 XO (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^-18 T^1.83 exp( 1748.54/T) , k_2a(T)=0.22×10^-19 T^2.19 exp( 1770.19/T) , k_3a(T)=0.88×10^-20 T^2.20 exp( 1513.82/T) (in units of cm 3 molecule −1 s −1 ).