Ab initio study of the OH + CH ₂O reaction: The effect of the OH··OCH ₂ complex on the H-abstraction kinetics

Kinetics for the reaction of OH radical with CH ₂O has been studied by single-point calculations at the CCSD(T)/6-311+G(3d f, 2p) level based on the geometries optimized at the B3LYP/6-311+G(3d f, 2p) and CCSD/6-311++G(d, p) levels. The rate constant for the reaction has been computed in the temperature range 200-3000 K by variational transition state theory including the significant effect of the multiple reflections above the OH··OCH ₂ complex. The predicted results can be represented by the expressions k ₁ = 2.45 × 10 ^-21T ^-2.98 exp(1750/T)cm ³ mol ^-1 s ^-1 (200-400 K) and 3.22 × 10 ^-18T ^2.11 exp(849/T) cm ³ mol ^-1 s ^-1 (4003000 K) for the H-abstraction process and k ₂ = 1.05 × 10 ^-17T ^1.63exp(-2156/T)cm ³ mol ^-1 s~' in the temperature range of 200-3000 K for the HO-addition process producing the OCH ₂OH radical. The predicted total rate constants (k ₁ + k ₂) can reproduce closely the recommended kinetic data for OH + CH ₂O over the entire range of temperature studied.