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 CH₂XO (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_{1{text{a}} }}(T)=0.32times {10^{-18 }}{T^{1.83 }}exp left( {1748.54/T} right) $ , $ {k_{2{text{a}} }}(T)=0.22times {10^{-19 }}{T^{2.19 }}exp left( {1770.19/T} right) $ , $ {k_{3{text{a}} }}(T)=0.88times {10^{-20 }}{T^{2.20 }}exp left( {1513.82/T} right) $ (in units of cm³ molecule^?1?s^?1).