The hydroxyl radical (OH) is one of the main oxidants of the atmosphere, controlling the lifetimes of volatile organic compounds (VOCs) and contributing to production of ozone and secondary organic aerosols (SOA). Methyl Ethyl Ketone (MEK) is the second most abundant ketone emitted to the atmosphere after acetone with both biogenic and anthropogenic sources in addition to secondary production as a product of VOC oxidation. Its reaction with OH is an order of magnitude greater than that for acetone, which makes it an important OH sink. While there have been multiple studies focused measurements of the rate constant for the reaction of MEK with OH radicals, there are discrepancies associated with measurements of the temperature dependence of this reaction. Measurements and theoretical calculations of the rate constant and potential energy surface of the OH + MEK reaction will be presented. Experiments were carried out using a low-pressure discharge flow tube coupled with laser-induced fluorescence detection of the OH radical. The measured rate constant for OH + MEK was found to be 1.1 ± 0.1 x 10-12 cm3 molecules-1 s-1 at 298 K, and an Arrhenius expression of k = (1.21 ± 0.29) x 10-12 exp [-(135 ± 95.9)/T]) was obtained from the measurements of the rate constant between 273 and 368 K. Theoretical calculations of the reaction’s potential energy surface were conducted in Gaussian 16 using the G4 composite method for each of the three reaction channels. The results suggest that the reaction’s mechanism involves hydrogen abstraction through hydrogen-bonded pre-reactive and post-reactive complexes. The results will be compared to previous measurements and theoretical studies of the rate constant for this and similar reactions.

Measurements of the temperature-dependent rate constant for the reaction of hydroxyl radical with methyl ethyl ketone

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