Watching a hydroperoxyalkyl radical (•QOOH) dissociate

Hansen, Anne S.; Bhagde, Trisha; Moore, III, Kevin B.; Moberg, Daniel R.; Jasper, Ahren W.; Georgievskii, Yuri; Vansco, Michael F.; Klippenstein, Stephen J.; Lester, Marsha I.

doi:10.1126/science.abj0412

DOE OSTI · 1812117

Watching a hydroperoxyalkyl radical (•QOOH) dissociate

Hansen, Anne S.·Bhagde, Trisha·Moore, III, Kevin B.·Moberg, Daniel R.·Jasper, Ahren W.·Georgievskii, Yuri·Vansco, Michael F.·Klippenstein, Stephen J.·Lester, Marsha I.

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Abstract

A prototypical hydroperoxyalkyl radical (•QOOH) intermediate, transiently formed in the oxidation of volatile organic compounds, was directly observed through its infrared fingerprint and energy-dependent unimolecular decay to hydroxyl radical and cyclic ether products. Direct time-domain measurements of •QOOH unimolecular dissociation rates over a wide range of energies were found to be in accord with those predicted theoretically using state-of-the-art electronic structure characterizations of the transition state barrier region. Unimolecular decay was enhanced by substantial heavy-atom tunneling involving O-O elongation and C-C-O angle contraction along the reaction pathway. Master equation modeling yielded a fully a priori prediction of the pressure-dependent thermal unimolecular dissociation rates for the •QOOH intermediate—again increased by heavy-atom tunneling—which are required for global models of atmospheric and combustion chemistry.

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Hansen, Anne S., Bhagde, Trisha, Moore, III, Kevin B., Moberg, Daniel R., Jasper, Ahren W., Georgievskii, Yuri, Vansco, Michael F., Klippenstein, Stephen J., Lester, Marsha I.. 2021-08-05. Watching a hydroperoxyalkyl radical (•QOOH) dissociate. https://doi.org/10.1126/science.abj0412

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