Welcome to the new version of CaltechAUTHORS. Login is currently restricted to library staff. If you notice any issues, please email coda@library.caltech.edu
Published June 20, 2013 | Supplemental Material
Journal Article Open

OH Radical-Initiated Chemistry of Isoprene in Aqueous Media. Atmospheric Implications


The fate of isoprene (2-methyl-1,3-butadiene, ISO) emissions into the atmosphere is not fully understood. Increasing awareness that ISO is only partially processed in the gas-phase has turned attention to its reactive uptake by fog, cloud, and aerosol droplets. A hydrophobic gas, ISO would preferentially partition to the surface rather than the bulk of aqueous media. Such media normally contain dissolved O_2 and water-soluble unsaturated organics and support •OH generation rates (from the solar photolysis of dissolved H_(2)O_2) that are several orders of magnitude larger than in the gas-phase. Thus, ISO should be converted therein to heavier products rather than into the C_4–C_5 volatile compounds produced in the gas-phase. Here we substantiate such a scenario by reporting that the λ > 305 nm photolysis of H_(2)O_2 in dilute aqueous ISO solutions yields C_(10)H_(15)OH species as primary products, whose formation both requires and is inhibited by O_2. A minimum of seven C_(10)H_(15)OH isomers are resolved by reverse-phase high-performance liquid chromatography and detected as MH^+ (m/z = 153) and MH^(+)-18 (m/z = 135) signals by electrospray ionization mass spectrometry. Our findings are consistent with the addition of •OH to ISO, followed by HO-ISO• reactions with ISO in competition with O_2, leading to second generation HO(ISO)_2• radicals that terminate as C_(10)H_(15)OH via β-H abstraction by O_2. We show that a significant fraction of gas-phase olefins should be converted into less volatile species via this process on wet airborne particles.

Additional Information

© 2013 American Chemical Society. Received: March 15, 2013; Revised: May 20, 2013; Published: May 22, 2013. This work was supported by NSF (U.S.A.) Grant AC-1238977.

Attached Files

Supplemental Material - jp4026267_si_001.pdf


Files (269.1 kB)
Name Size Download all
269.1 kB Preview Download

Additional details

August 19, 2023
October 24, 2023