Theoretical study of the reactions of hydrogen atom with methyl and ethyl hydroperoxides

Abstract

An ab initio dynamic study of the reactions of H atom with CH3OOH and CH3CH2OOH was performed over the temperature range of 250–1500 K. The geometries of all stationary points were optimised at the MP2, B3LYP and M06-2X theories. The final electronic energies for all species were refined by the CCSD(T) and QCISD(T) methods. The rate coefficients were calculated using canonical variational transition state theory (CVT) with small-curvature tunnelling (SCT) correction or the multichannel Rice−Ramsperger−Kassel−Marcus (RRKM) and CVT methods. The results showed that the channel of H-abstraction from OH group is dominant channel only at temperature less than 350 K. With the temperature higher than 350 K, the OH-transfer channel becomes dominant channel. For the CH3OOH + H reaction, the channel to produce H2 + CH2O + OH becomes the dominant channel at temperature higher than 800 K. For the CH3CH2OOH + H reaction, the channel to produce H2 + CH3CH2O + OH is important at temperature less than 600 K and has a maximum branching ratio of 0.3 around 350 K.