PRODUCTS OF THE GAS-PHASE REACTIONS OF O-3 WITH ALKENES

The products of the gas-phase reactions of O-3 with 1-pentene, 1-hexene, 1-heptene, 1-octene, 2,3-dimethyl-1-butene, cyclopentene, and 1-methylcyclohexene have been investigated at room temperature and 740 Torr total pressure of air in the presence of cyclohexane or n-octane to scavenge OH radicals. Products were identified and quantified by gas chromatography and in situ Fourier transform infrared absorption spectroscopy. In the presence of cyclo-hexane, cyclohexanone and cyclohexanol were observed as products, showing the formation of OH radicals from these O-3 reactions. The OH radical formation yields derived were as follows: 1-pentene, 0.37; 1-hexene, 0.32; 1-heptene, 0.27; 1-octene, 0.18; 2,3-dimethyl-1-butene, 0.50; cyclopentene, 0.61; and 1-methylcyclohexene, 0.90, all with estimated overall uncertainties of a factor of similar to 1.5. The carbonyl products identified and quantified were as follows: from 1-pentene: butanal, 0.541 +/- 0.065, and HCHO, 0.595 +/- 0.055; from 1-hexene: pentanal, 0.518 +/- 0.095, and HCHO, 0.575 +/- 0.057; from 1-heptene: hexanal, 0.582 +/- 0.078, and HCHO, 0.533 +/- 0.049; from 1-octene: heptanal, 0.527 +/- 0.070, and HCHO, 0.519 +/- 0.054; from 2,3-dimethyl-1-butene: 3-methyl-2-butanone, 0.391 +/- 0.050, and HCHO, 0.776 +/- 0.071; from cyclopentene: butanal, 0.195 +/- 0.027; and from 1-methylcyclohexene: 5-acetylpentanal, 0.100 +/- 0.024. For the 1-alkenes, the sum of the two carbonyl products expected from the decomposition of the initially formed primary ozonide is 1.1 +/- 0.1, consistent with the presently believed reaction mechanism. The 3-methyl-2-butanone and HCHO yields from 2,3-dimethyl-1-butene show that the primary ozonide decomposes preferentially to HCHO plus the dialkyl-substituted [(CH3)(2)CHC(CH3)OO]* biradical rather than to 3-methyl-2-butanoneplus the [CH2OO]* biradical.