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

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 a-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 x 10(-14) and 2.56 x 10(-14) cm(3) 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.