Carbonyl Oxides

Carbonyl Oxides in the Atmosphere

Carbonyl oxides (sometimes referred to as Criegee intermediates) are a class of short lived reactive intermediates formed in the reaction of alkenes with ozone in the atmosphere. Carbonyl oxides are a critical contributor to atmospheric composition: they are a major source of OH radicals, accounting for approximately a third of OH radical production in the daytime and essentially all of OH production at night. Further, their bimolecular reactions (particularly with water) are a source of low volatility species that may be implicated in secondary organic aerosol formation.

Laser Spectroscopy of Carbonyl Oxides

Using an alternative synthetic method relying on photolysis of a dioodo substituted organic compound, I was able to make collisionally stabilized carbonyl oxides in sufficiently high concentrations that they may be probed directly. I then used infrared action spectroscopy to study their unimolecular decay. In this method, the carbonyl oxide is vibrationally excited, providing energy that induces the unimolecular decay reaction and produces OH. The resulting OH radicals are detected using laser induced fluorescence.

Key Results

With this method, I was able to measure infrared action spectra and OH appearance rates of a number of carbonyl oxides, including prototypical carbonyl oxides (e.g. small, alkyl substituted species). Most recently I achieved the first direct detection of the predominant carbonyl oxide formed from the ozonolysis of isoprene, methyl vinyl ketone oxide. The results of this work have substantially improved our understanding of carbonyl oxide chemistry in the atmosphere, helping us to determine when unimolecular decay will dominate the fate of carbonyl oxides, and when bimolecular reactions may be more important

Relevant Publications

Barber, V.P., Esposito, V.J., Trabelsi, T., †McHenry, T., Francisco, J., Lester, M.I., Experimental and computational investigation of vinoxy and 1-methylvinoxy radicals from the unimolecular decay of alkyl-substituted Criegee intermediates. Chem. Phys. Lett., 2020. 751, 137478 (†Undergraduate Coauthor)
Barber, V.P., Hansen, A.S., Klippenstein, S.J., Lester, M.I., Experimental and Theoretical Studies of the Doubly Substituted Methyl-Ethyl Criegee Intermediate: Infrared Action Spectroscopy and Unimolecular Decay to OH Radical Products. J. Chem Phys., 2020. 152(9), 094301
Featured as “Editor’s Pick” in J. Chem. Phys.
Barber, V.P., Pandit, S., Esposito, V.J., McCoy, A.B., Lester, M.I., IR Action Spectroscopy of the Syn-CH₃CHOO Criegee Intermediate in the Fundamental CH Stretch Region: Tunneling to OH Products. J. Phys. Chem. A. 2019. 123(13), 2559
Barber, V.P., Pandit, S., Green, A.M., Trongsiriwat, N., Walsh, P.J., Klippenstein, S.J., Lester, M.I., Four Carbon Criegee Intermediate from Isoprene Ozonolysis: Methyl Vinyl Ketone Oxide Synthesis, Infrared Spectrum, and OH Production. J. Am. Chem. Soc., 2018. 140(34), 10866
*Green, A.M., *Barber, V.P., Fang, Y., Klippenstein, S.J., Lester, M.I. Unimolecular Decay of a Selectively Deuterated Criegee Intermediate to OD Radical Products: Importance of Tunneling. Proc. Natl. Acad. Sci. U.S.A., 2017. 114(47), 12372 (*Equal contributions)
Fang, Y., Barber, V.P., Klippenstein, S.J., McCoy, A.B., Lester, M.I. Tunneling Effects in the Unimolecular Decay of (CH₃)₂COO Criegee Intermediates to OH Radical Products. J. Chem. Phys., 2017. 146(13), 134307
Featured as “Editor’s Pick” in J. Chem. Phys.
Fang, Y., Barber, V.P., Klippenstein, S.J., McCoy, A.B., Lester, M.I. Deep Tunneling in the Unimolecular Decay of CH₃CHOO Criegee Intermediates to OH Radical Products. J. Chem. Phys., 2016. 145(23), 234308
Fang, Y., Liu, F., Barber, V.P., Klippenstein, S.J., McCoy, A.B., Lester, M.I. Communication: Real Time Observation of Unimolecular Decay of Criegee Intermediates to OH Radical Products. J. Chem. Phys., 2016. 114(6), 061102

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