Elementary radical reactions and autoignition

The kinetics of the elementary reactions involved in the low-temperature combustion of alkanes are reviewed. The reactions are centred on the alkyl radical and its decomposition, recombination and reactions with O2. A combination of theory, modelling and direct measurements, using especially laser flash photolysis, have played key roles in the characterisation of all three reaction types. A remaining area of uncertainty is the mechanism of the R + O2 reaction and the interplay of channels leading to the alkyl hydroperoxyl radical and to the conjugate alkene + HO2. A mechanism based on two electronic surfaces is proposed.This Polanyi memorial lecture was given when the 1994 Polanyi medal was presented to Professor M. J. Pilling at the 13th International Gas Kinetics Symposium in September 1994 in Dublin.

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