The point of oxygen attack in the combustion of hydrocarbons I. The origin of carbon monoxide

Abstract

An investigation is described of the slow combustion of some 14 C-labelled hydrocarbons. This work was designed to throw light on the point of initial attack in gaseous oxidation processes. Methods have been devised for the synthesis of 2-methylpentane labelled in each of the skeletal positions in turn. Combustion of these compounds with an insufficiency of oxygen was carried out at 242 and 380°C and the carbon monoxide formed was further oxidized by preferential combustion over copper oxide. The specific activity of the resulting carbon dioxide was then determined in the liquid phase after absorption in a solution of lithium phenyl. At both temperatures carbon monoxide was found to be derived principally from the 3- and 4-positions. Oxidation at a tertiary centre is unlikely, however, to lead to production of appreciable amounts of carbon monoxide and this may account for the low yield s from the 2-position. Nevertheless, it is concluded that the relative amounts of carbon monoxide formed from the 1-, 3-, 4- and 5-positions provide a reliable indication of the relative probabilities of initial attack at these points.