Reactions of primary and secondary butoxy radicals in oxygen at atmospheric pressure

Abstract

The reaction pathways of n-butoxy and s-butoxy radicals have been investigated by TLC and HPLC analysis of end products, particularly peroxides and carbonyl compounds. The butoxy radicals were produced by the pyrolysis of very low concentrations of the corresponding dibutylperoxide in an atmosphere of oxygen and nitrogen, at atmospheric pressure. The decomposition reaction (3) s-BuO → C2H5 + CH3CHO and the reaction (2) s-BuO + O2 → HO2 + CH3COC2H5 have been studied, and the ratio k3/k2 has been determined in the temperature range 363–503 K by kinetic modeling of the formation of the observed acetaldehyde and methylethylketone. The rate constant k3 obtained was: A good agreement was observed between experimental data and RRKM theory. The implications of the results for atmospheric chemistry and combustion are discussed. At room temperature, the reaction with O2, yielding HO2 radicals and methylethylketone is, by far, the main channel for s-BuO radicals. In the field of low temperature combustion, the decomposition of s-BuO radicals producing C2H5 and CH3CHO is the main pathway; the route s-BuO + O2 decreases tremendously in importance as the temperature is raised above 393 K.