Quantitative studies of the role of alkenes during the combustion of alkanes

Abstract

Studies of the combustion of n-butane in the presence of small amounts of [1-14C]but-1-ene and [2-14C]but-2-ene have enabled the role and importance of the two alkenes in the oxidation of the alkane to be determined quantitatively. Thus at 315°, at a stage when the reaction rate has started to decline, over one-third of the n-butane which has reacted has been oxidized to butenes and nearly two-thirds of these two alkenes has reacted further to give other products. All the larger-ring oxa-heterocyclic products and the major part of the oxirans arise by a mechanism not involving the intermediate formation of C4 alkenes but a substantial proportion of the 2-ethyloxiran and 2,3-dimethyloxiran are formed by the direct oxidation of but-1-ene and but-2-ene respectively. About one-quarter of the C4 ketones and an appreciable part of the lower molecular weight aldehydes also appear to be formed by an alkenic route. The general conclusion which emerges is that at the temperature concerned butenes play an important but not overwhelming role as intermediates in the combustion of n-butane.