ChemInform Abstract: Oxidation of Allyl Radicals: Kinetic Parameters for the Reactions of Allyl Radicals with HO2 and O2 Between 400 and 480 °C.

Abstract

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 °C. Propene was added to the mixtures of DMP and O2 in order to monitor [HO2] 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 reactions (9) and (10). [graphic omitted] + HO2→ CO + product (9), [graphic omitted] + HO2→ C3H6+ HO2(10) At 400 °C, k9= 3.95 × 109 and k10= 1.42 × 109 dm3 mol–1 s–1 and both show a slight increase (within experimental error) with temperature, 15% and 30%, respectively, at 480 °C.Strong evidence is obtained for the formation of CO in the reaction between allyl radicals and O2[reaction (15)] and values of A15= 109.4 ± 0.6 dm3 mol–1 s–1 and E15= 79 ± 8 kJ mol–1 are obtained. [graphic omitted] + O2→ CO + products (15)The mechanisms 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 the reverse of the chain initiation reaction (16). C3H6+ O2→ [graphic omitted] + HO2(16)The available kinetic data for the reaction between allyl radicals and O2 are summarised.