THE PHOTOCHEMICAL OXIDATION OF ALDEHYDES IN THE GASEOUS PHASE: PART II. THE KINETICS OF THE PHOTOCHEMICAL OXIDATION OF PROPIONALDEHYDE

Abstract

The photochemical oxidation of propionaldehyde has been studied in the gaseous phase at 23 °C. and a wavelength of 3130 Å. With pressures of oxygen varying from 0.3 mm. to 100 mm. Hg it has been established that the reaction obeys the same kinetic law as that found for the corresponding reaction with acetaldehyde, namely:[Formula: see text]where k3 is the velocity constant for the propagating reaction [3]:[Formula: see text]and k6 is the velocity constant for the terminating reaction [6]:[Formula: see text][Formula: see text]is the rate of initiation and it is regarded as being a composite quantity representing the rate of formation of propionyl radicals, which are thought to be the initiators of the oxidation chain. The propionyl radicals are thought to be formed by two processes: (a) from the subsequent reactions of free radicals produced in the primary free radical process which occurs when propionaldehyde absorbs a quantum of radiation at 3130 Å, and (b) from the subsequent reactions, with oxygen, of excited states of propionaldehyde, which are also thought to be formed by the absorption of light of wavelength 3130 Å.