We report that gaseous isoprene ISO(g) is oxidized into soluble species on the surface of aqueous acidic FeCl2 solutions simultaneously exposed to H2O2(g). In our experiments, ISO(g) and/or H2O2(g) streams intersect aqueous pH ∼ 2 FeCl2 microjets for ∼10 μs. The products formed in these reactive encounters are identified in situ via online electrospray ionization mass spectrometry. We found that the (ISO)nH+ oligomers generated from ISO(g) on the surface of pH < 4 water are oxidized into myriad products whose combined yields exceed 5%. MS2 analysis reveals that the positive ions derived from the protonation of neutral products split H2O and O neutrals, whereas the less abundant negative carboxylate ion products undergo CO, H2O, and CO2 losses. Significantly, all products are fully quenched by ·OH scavenger tert-butyl alcohol. These results are consistent with an oxidation process initiated by the addition of ·OH from (Fe2+(aq) + H2O2(g)) to (ISO)nH+, followed by fast reactions involving dissolved H2O2, HO2·, and O2 that lead to polyols; carbonyls; and, to a lesser extent, carboxylic acids. Our experiments demonstrate that gas-phase olefins are oxidized upon colliding on the surface of Fe-containing acidic aqueous media under typical tropospheric conditions.
Fenton oxidation of gaseous isoprene on aqueous surfaces / F.R. Kameel, F. Riboni, M.R. Hoffmann, S. Enami, A.J. Colussi. - In: JOURNAL OF PHYSICAL CHEMISTRY. C. - ISSN 1932-7447. - 118:50(2014 Dec 18), pp. 29151-29158. [10.1021/jp505010e]
Fenton oxidation of gaseous isoprene on aqueous surfaces
F. RiboniSecondo
;
2014
Abstract
We report that gaseous isoprene ISO(g) is oxidized into soluble species on the surface of aqueous acidic FeCl2 solutions simultaneously exposed to H2O2(g). In our experiments, ISO(g) and/or H2O2(g) streams intersect aqueous pH ∼ 2 FeCl2 microjets for ∼10 μs. The products formed in these reactive encounters are identified in situ via online electrospray ionization mass spectrometry. We found that the (ISO)nH+ oligomers generated from ISO(g) on the surface of pH < 4 water are oxidized into myriad products whose combined yields exceed 5%. MS2 analysis reveals that the positive ions derived from the protonation of neutral products split H2O and O neutrals, whereas the less abundant negative carboxylate ion products undergo CO, H2O, and CO2 losses. Significantly, all products are fully quenched by ·OH scavenger tert-butyl alcohol. These results are consistent with an oxidation process initiated by the addition of ·OH from (Fe2+(aq) + H2O2(g)) to (ISO)nH+, followed by fast reactions involving dissolved H2O2, HO2·, and O2 that lead to polyols; carbonyls; and, to a lesser extent, carboxylic acids. Our experiments demonstrate that gas-phase olefins are oxidized upon colliding on the surface of Fe-containing acidic aqueous media under typical tropospheric conditions.File | Dimensione | Formato | |
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