The point of oxygen attack in the combustion of hydrocarbons II. The formation and origin of ketones

Abstract

Studies have been made of the extent and mechanism of formation of ketones during the slow combustion of 2-methylpentane. With the aid of 14C-labelling at different skeletal positions, it has been shown, by separation and degradation of the various combustion products, that the carbonyl carbon atom in the ketone is always derived from the 2-position in the hydrocarbon. Acetone and methyl n-propyl ketone probably arise by a mechanism involving the abstraction of hydrogen by tertiary peroxy radicals from other hydrocarbon molecules. Tracer experiments show, however, that the methyl ethyl ketone formed incorporates the 2- and 3-positions but not the 4- and 5-positions in the hydrocarbon, and it is evident that some form of intramolecular rearrangement of tertiary peroxy radicals must take place.