Direct study of peroxy radical unimolecular reactions Rabi Chhantyal-Pun University of Nottingham, UK
Biogenic volatile organic compounds such as isoprene and pinenes emitted by plants play an important role in the atmosphere by setting the background chemistry. These compounds predominantly undergo OH radical initiated oxidation in the troposphere to produce peroxy radicals which are key intermediates. Peroxy radicals react with nitric oxide to form nitrogen dioxide and eventually ozone, which lead to reduction in air quality. Autoxidation has been suggested to be the dominant peroxy radical reaction pathway in the low nitric oxide environments.[1] Recently, autoxidation of peroxy radicals has been shown to initiate formation of highly oxygenated molecules which provide a purely biogenic pathway for nucleation and aerosol formation.[2] Such pathwaysare critical to our understanding of pre-industrial, present and future environments. Autoxidation involves intramolecular H- atom abstraction by the peroxy radical terminal oxygen atom, followed by addition of oxygen molecule to form another peroxy radial. The intramolecular H- atom transfer reaction is expected to be highly structure dependent. Near infrared cavity ring-down spectroscopy (CRDS) of peroxy radicals has been shown to provide structure specific probe and is ideal for kinetic measurements.[3] A new CRDS apparatus being developed at Nottingham to provide direct time resolved measurement of the unimolecular H- atom transfer reaction of peroxy radical will be presented. References 1. Crounse et al. J. Phys. Chem. Lett. 2013, 4, 3513 2. Kirkby et al. Nature 2016, 533, 521 3. Chhantyal-Pun et al. J. Phys. Chem. Lett. 2010, 1, 1846
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