Products of the gas-phase reactions of o3 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 Torrtotal 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 cyclohexane, 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 ∼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 showthatthe primary ozonide decomposes preferentially to HCHO plus the dialkyl-substituted [(CH 3 ) 2 CHC(CH 3 )OO] * biradical rather than to 3-methyl-2-butanone plus the [CH 2 00] * biradical.