Mechanism and kinetics for the reactions of methacrolein and methyl vinyl ketone with HO2 radical

Abstract

The high-level theoretical study on the reactions of methacrolein and methyl vinyl ketone with hydroperoxyl radical was carried out using the M06-2X method in conjunction with the 6-311+G(2df,2pd) basis sets. For the two reactions, all possible addition and abstraction channels initiate from the reactant complexes. The most favorable reaction channel is the concerted addition of the terminal O atom of HO₂ radical to the aldehyde-C (or carbonyl-C) and H-transfer from HO₂ to the aldehyde-O (or carbonyl-O) forming the α-hydroxyalkenylperoxy radical. For the methacrolein + HO₂ and methyl vinyl ketone + HO₂ reactions, the calculated rate constants decrease as the temperature increases from 200 K to 500 K, and at 298 K, they are 1.34 × 10⁻¹⁴ and 2.56 × 10⁻¹⁴ cm³ molecule⁻¹ s⁻¹, respectively. The calculated results are close to the previous theoretical and experimental observations for the reactions of HO₂ radical with formaldehyde, acetaldehyde, and acetone.