Chain Propagation in the Oxidation of Alkyl Radicals

During the gaseous oxidation of alkanes, chain propagation occurs by oxidation of alkyl radicals and their regeneration from the alkane. Routes involving intermolecular and intramolecular hydrogen abstraction by alkylperoxy radicals compete with routes via alkenes and hydroperoxy radicals. Calculation of the thermodynamic and kinetic parameters of the steps involved has enabled a single general scheme for chain propagation to be devised and the relative importances of the various chains to be assessed. At temperatures of ca. 550°K. the route via alkenes and hydroperoxy radicals is unimportant during the oxidation of large alkyl radicals but is more important for small radicals. The reasons for this are discussed.