Theoretical studies of the reaction of hydroperoxy radicals (HO2) with ethyl peroxy (CH3CH2O2), acetyl peroxy (CH3C(O)O2), and acetonyl peroxy (CH3C(O)CH2O2) radicals

Product yield studies indicate that the reaction of organic peroxy radicals (RO2) with hydroperoxy radicals (HO2) may proceed via four reaction channels:(R1a)RO2 + HO2 → ROOH + O2(R1b)RO2 + HO2 → ROH + O3(R1c)RO2 + HO2 → RO + OH + O2(R1d)RO2 + HO2 → R′CHO + H2O + O2While (R1a) is the dominant pathway for alkyl peroxy radicals, it has been reported that acetyl peroxy radicals (R = CH3C(O)) react via (R1a), (R1b) and (R1c), while acetonyl peroxy radicals (R = CH3C(O)CH2)) reacts via (R1a) and (R1c). In this work, quantum calculations using the CBS-QB3 method coupled with Master equation analysis and kinetic simulations have been used to propose reaction mechanisms for the formation of the products observed in reaction (R1) for ethyl peroxy (R = CH3CH2), acetyl peroxy, and acetonyl peroxy radicals. (R1a) is found to proceed via hydrogen atom transfer, while (R1b) and (R1c) both proceed through a hydrotetroxide intermediate. The calculations demonstrate that the mechanism is consistent with the experimentally measured product yields, and that (R1b) and (R1c) may also be significant for structurally similar organic peroxy radicals. The implications of these calculations are discussed.