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Published December 18, 2014 | Supplemental Material
Journal Article Open

Fenton Oxidation of Gaseous Isoprene on Aqueous Surfaces


We report that gaseous isoprene ISO(g) is oxidized into soluble species on the surface of aqueous acidic FeCl_2 solutions simultaneously exposed to H_2O_2(g). In our experiments, ISO(g) and/or H_2O_2(g) streams intersect aqueous pH 2 FeCl_2 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%. MS^2 analysis reveals that the positive ions derived from the protonation of neutral products split H_2O and O neutrals, whereas the less abundant negative carboxylate ion products undergo CO, H_2O, and CO_2 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 (Fe^(2+)(aq) + H_2O_2(g)) to (ISO)nH^+, followed by fast reactions involving dissolved H_2O_2, HO_2·, and O_2 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.

Additional Information

© 2014 American Chemical Society. Received: May 21, 2014; revised: July 9, 2014. F.R.K., M.R.H., and A.J.C. acknowledge financial support from the National Science Foundation (U.S.A.) Grant AC-1238977. F.R. gratefully acknowledges her tutor, Prof. E. Selli, and financial support from the Doctorate School in Chemistry of the University of Milan. S.E. is grateful to Kurita Water and Environment Foundation and the Japan Science and Technology Agency (JST) PRESTO program.

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