FORMATION YIELDS OF METHYL VINYL KETONE AND METHACROLEIN FROM THE GAS-PHASE REACTION OF O3 WITH ISOPRENE

The formation yields of methyl vinyl ketone and methacrolein from the gas-phase reaction of O3 with isoprene were determined at 296 +/- 2 K and 740 Torr total pressure of air. Sufficient cyclohexane was added to the reactant mixture to scavenge >97 % of the OH radicals formed in the O3-isoprene reaction, and secondary reactions of 03 with methyl vinyl ketone and methacrolein were taken into account. The formation yields obtained were 0.159 +/- 0.013 for methyl vinyl ketone and 0.387 +/- 0.030 for methacrolein. Experiments were also carried out in the absence of added cyclohexane, and the methyl vinyl ketone and methacrolein data were consistent with formation from both the OH radical and O3 reactions with isoprene. The data obtained are compared with the literature data and the reaction mechanism discussed.