Reactions of nonequilibrium oxygen plasmas with liquid olefins

The oxidation of 13 liquid olefins with either high-voltage or radiofrequency (RF) glow discharges has been studied The reactions were carried out by making the oxygen plasma reach the low vapor pressure substrate. Product formation has proved to be selective-epoxides, aldehydes, ketones, and low quantities of carboxylic acids being the most important species. Fragmentation products were only observed in the traps of the RF system for the most volatile olefin of this study. This indicates that, except for this case, the most relevant interaction of this study has been the heterogeneous reaction of the plasma with the liquid. Total conversion, i.e., mass transformed against initial mass of substrate, has been studied as a function of temperature of the liquid and oxygen flow rate in the reactor, this ranging from 15 to 53.6 mmol/hr in the high-voltage system and 13 to 270 mmol/hr in the RF device. The optimum conversions were 27 to 99%. A correlation between these results and the behavior of the O(P-3) population in the discharge allows us to conclude that this is the most relevant species to the oxidation process. A discussion relating the structures of the olefins with the composition of the mixtures produced by the oxidation is also presented.