Alkyl radicals rule the low temperature oxidation of long chain aldehydes

A reliable and simple approach for the characterization of the low temperature kinetics of C3-C4 and heavier aldehydes was proposed. The high reactivity of the weakly bound aldehydic H-atom lresulted in the predominant formation of carbonyl radicals. While acetyl-radical addition to oxygen was a key step in the low temperature reactivity of acetaldehyde heavier carbonyl radicals were rapidly decomposed to CO and alkyl radicals. Comprehensive kinetic analysis of the low temperature oxidation data (including cool flames of acetaldehyde oxidation of propanal n-butanal and iso-butanal in jet-stirred reactor validates and supports the kinetic model as well as the assumption of the direct decomposition of heavy carbonyl radicals.