Inhibition of the thin-film oxidation of n-dodecane by diphenylamine

Abstract

The inhibition by diphenylamine (DPA) of the oxidation of a thin film of n-dodecane has been studied over the temperature range 180–230 °C by following the consumption of gaseous oxygen, the disappearance of the inhibitor and the formation of peroxides. At the start of the reaction there is an induction period which increases linearly with the initial concentration of inhibitor. During the first part of this induction period there is apparently no change in the concentration of DPA, but it has all been consumed by its end, although there is only a negligible decrease in the absorption at 1600 and 3400 cm^–1 due to N—H. Thus it is concluded that abstraction of the amino hydrogen cannot be involved in the inhibition mechanism under the present experimental conditions, and it is suggested that the first step is probably an electron-transfer reaction between an alkyl radical and the inhibitor.