Multichannel RRKM-TST and CVT rate constant calculations for reactions of CH_2OH or CH_3O with HO_2

摘要

The kinetics and mechanism of the gas-phase reactions between hydroxy methyl radical (CH_2OH) or methoxy radical (CH_3O) with hydroproxy radical (HO_2) have been theoretically investigated on their lowest singlet and triplet surfaces. Our investigations indicate the presence of one deep potential well on the singlet surface of each of these systems that play crucial roles on their kinetics. We have shown that the major products of CH_2OH + HO_2 system are HCOOH, H_2O, H_2O_2, and CH_2O and for CH_3O + HO_2 system are CH_3OH and O_2. Multichannel RRKM-TST calculations have been carried out to calculate the individual rate constants for those channels proceed through the formation of activated adducts on the singlet surfaces. The rate constants for direct hydrogen abstraction reactions on the singlet and triplet surfaces were calculated by means of direct-dynamics canonical variational transition-state theory with small curvature approximation for the tunneling.