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Published February 20, 2014 | Supplemental Material
Journal Article Open

Gas Phase Production and Loss of Isoprene Epoxydiols


Isoprene epoxydiols (IEPOX) form in high yields from the OH-initiated oxidation of isoprene under low-NO conditions. These compounds contribute significantly to secondary organic aerosol formation. Their gas-phase chemistry has, however, remained largely unexplored. In this study, we characterize the formation of IEPOX isomers from the oxidation of isoprene by OH. We find that cis-β- and trans-β-IEPOX are the dominant isomers produced, and that they are created in an approximate ratio of 1:2 from the low-NO oxidation of isoprene. Three isomers of IEPOX, including cis-β- and trans-β, were synthesized and oxidized by OH in environmental chambers under high- and low-NO conditions. We find that IEPOX reacts with OH at 299 K with rate coefficients of (0.84 ± 0.07) × 10^(–11), (1.52 ± 0.07) × 10^(–11), and (0.98 ± 0.05) × 10^(–11) cm^3 molecule^(–1) s^(–1) for the δ1, cis-β, and trans-β isomers. Finally, yields of the first-generation products of IEPOX + OH oxidation were measured, and a new mechanism of IEPOX oxidation is proposed here to account for the observed products. The substantial yield of glyoxal and methylglyoxal from IEPOX oxidation may help explain elevated levels of those compounds observed in low-NO environments with high isoprene emissions.

Additional Information

© 2014 American Chemical Society. Received: November 1, 2013; Revised: January 28, 2014; Published: January 29, 2014. The authors would like to thank Prof. Jason D. Surratt for correspondence regarding the synthesis of IEPOX and the National Science Foundation (AGS 1240604) for their support of this research.

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