Inert Gas Effects in the Oxidation of Hexane

Abstract

ACCORDING to one scheme of hydrocarbon oxidation¹, a link in the gaseous reaction chain at low temperatures is the formation of a peroxide radical: followed by: (The formation of RO₂ appears to have been first proposed for the low-temperature oxidation of gaseous higher alkanes by A. R. Ubbelohde¹. Other authors have proposed variants which still involve (1) as a step in the oxidation mechanisms.) Until it can be dissipated, for example, by collisions with other molecules, the energy of reaction must be stored for a short time in the RO₂^* radical. Various physical properties² of the hydrocarbon molecule may facilitate this storage of internal energy in reaction intermediates for much longer periods than would be possible in the combination of simpler groups, as in The energy stored can be utilized in a subsequent process in the reaction chain, such as reaction (2), provided that this reaction can occur before collisions in the gas phase favour the competing deactivation reaction: where X is any third body. A possibility of this kind has been put forward (ref. 1, p. 373) as one of the factors which explain the much greater influence on reaction velocity of increasing the concentration of hydrocarbon rather than the concentration of oxygen.