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Published June 12, 2014 | Supplemental Material
Journal Article Open

In Situ Mass Spectrometric Detection of Interfacial Intermediates in the Oxidation of RCOOH(aq) by Gas-Phase OH-Radicals


Products and intermediates of the oxidation of aqueous alkanoic acids initiated by gas-phase hydroxyl radicals, ·OH(g), at the air–water interface were detected by mass spectrometry in a novel setup under various experimental conditions. Exposure of submillimolar RCOOH (R = methyl, n-pentyl, n-heptyl) aqueous microjets to ~10 ns ·OH(g) pulses from the 266 nm laser flash photolysis of O_3(g)/O_2(g)/H_2O(g) mixtures yielded an array of interfacial species that were unambiguously and simultaneously identified in situ by online electrospray mass spectrometry. We found that peroxyl radicals R(−H)(COO^–)OO· react within 50 μs to produce alcohols R(−H)(COO^–)OH and carbonyls R(−2H)(COO–)═O via competitive Russell and Bennett–Summers mechanisms. We confirmed the formation of hydroperoxides R(−H)(COO^–)OOH in experiments performed in D_2O. To our knowledge, this is the first report on the prompt and simultaneous detection of products and peroxyl/peroxide intermediates in the heterogeneous oxidation of aqueous organics initiated by ·OH(g).

Additional Information

© 2014 American Chemical Society. Publication Date (Web): May 19, 2014. Received: April 7, 2014. Revised: May 11, 2014. Published: May 19, 2014. S.E. is grateful to Kurita Water and Environment Foundation and the Japan Science and Technology Agency (JST) PRESTO program. S.E. also thanks Prof. Hiroshi Masuhara and Dr. Yosuke Sakamoto for stimulating discussions. M.R.H. and A.J.C. acknowledge support from the National Science Foundation (U.S.A.) Grant AC-1238977. The authors declare no competing financial interest.

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