Oxidation of Allyl Radicals: Kinetic Parameters for the Reactions of Allyl Radicals with HO2 and O2 between 400 and 480 deg C

Article abstract of DOI:10.1039/ft9918702361

The decomposition of 4,4-dimethylpent-1-ene (DMP) in the presence of O2 has been used as a source of allyl and HO2 radicals between 400 and 480 deg C.Propene was added to the mixtures of DMP and O2 in order to monitor from the yields of propene oxide by use of the known value of k₁₄.HO2 + C3H6 -> C3H6O + OH (14).From measurements of the initial yields of CO, hexa-1,5-diene and propene oxide over a range of mixture composition, rate constants have been obtained for reaction (9) and (10). <*>CH2CHCH2 + HO2 -> CO + product (9); <*>CH2CHCH2 + HO2 -> C3H6 + HO2 (10).At 400 deg C, k₉ = 3.95 x 10⁹ and k₁₀ = 1.42 x 10⁹ dm³ mol^-1 s^-1 and both show a slight increase (within experimental error) with temperature, 15percent and 30percent, repectively, at 480 deg C.Strong evidence is obtained for the formation of CO in the reaction between allyl radicals and O2 and values of A₁₅ = 10^{9.4 +/- 0.6} dm³ mol^-1 s^-1 and E₁₅ = 79 +/- 8 kJ mol^-1 are obtained. <*>CH2CHCH2 + O2 -> CO + products (15).The mechanism of reactions (10) and (15) are discussed.Based on current thermochemistry it is shown by calculation that reaction (10) probably occurs only to a minor extent through a direct H-atom abstraction route which is reverse of the chain initiation reaction (16).C3H6 + O2 -> <*>CH2CHCH2 + HO2 (16).The available kinetic data for the reaction between allyl radicals and O2 are summarised.

Full text of DOI:10.1039/ft9918702361

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