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Published December 14, 2016 | Supplemental Material
Journal Article Open

Extensive H-atom abstraction from benzoate by OH-radicals at the air–water interface


Much is known about OH-radical chemistry in the gas-phase and bulk water. Important atmospheric and biological processes, however, involve little investigated OH-radical reactions at aqueous interfaces with hydrophobic media. Here, we report the online mass-specific identification of the products and intermediates generated on the surface of aqueous (H_2O, D_2O) benzoate-h5 and -d5 microjets by ∼8 ns ˙OH(g) pulses in air at 1 atm. Isotopic labeling lets us unambiguously identify the phenylperoxyl radicals that ensue H-abstraction from the aromatic ring and establish a lower bound (>26%) to this process as it takes place in the interfacial water nanolayers probed by our experiments. The significant extent of H-abstraction vs. its negligible contribution both in the gas-phase and bulk water underscores the unique properties of the air–water interface as a reaction medium. The enhancement of H-atom abstraction in interfacial water is ascribed, in part, to the relative destabilization of a more polar transition state for OH-radical addition vs. H-abstraction due to incomplete hydration at the low water densities prevalent therein.

Additional Information

© 2016 the Owner Societies. Received 28th September 2016 , Accepted 1st November 2016. First published on the web 2nd November 2016. S. E. is grateful to the Hakubi Project of Kyoto University, the Iwatani Naoji Foundation's Research Grant and JSPS KAKENHI grant number 15H05328. M. R. H. and A. J. C. acknowledge support from the National Science Foundation (U.S.A.) Grant AC-1238977.

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