SURFACE-REACTIONS OF OXYGEN IONS .3. OXIDATION OF ALKANES BY O-3(-) ON MGO

Ozonide ions on MgO reacted with C1 to C4 alkanes at 25°C with half-lives between 1.7 and 5.2 min. A stoichiometry of one alkane molecule reacted per one O3- ion was determined. Following the reactions, only ethane gave an appreciable amount of gas phase product (ethylene) at 25°C; however, upon heating the samples to elevated temperatures, other hydrocarbons and CO2 were obtained. At intermediate temperatures the corresponding C2 to C4 alkenes were the principal products, although the yields were less than observed in the corresponding reactions with O-. The presence of gas phase oxygen during the initial reaction suppressed the formation of these alkenes. Infrared spectra of the surface complexes indicate that the reaction of O3- with ethane at 25°C resulted in the formation of carbonate and ethoxide ions. At 150°C the ethoxide ions decreased in concentration and acetate ions were formed. The acetate ions, as well as the carbonate ions, decomposed at elevated temperatures. The initial step in the reaction of O3- with alkanes is believed to be hydrogen atom abstraction, with the alkyl radical either forming an alkoxide ion or an alkyl peroxy radical. The alkoxide ion is largely responsible for the formation of the corresponding alkene, and the peroxy radical, as well as other oxidation products, result in the formation of CO2 and CH4. © 1979 American Chemical Society.