Research Areas

Autoxidation Chemistry: Recently, autoxidation has been shown to be the dominant loss pathway for biogenic alkenes such as isoprene and terpenes in remote forested areas. As various government policies are implemented to achieve the goals of net zero carbon emissions, autoxidation is expected to play a greater role in oxidation chemistry of rural as well as urban areas too. Autoxidation involves peroxy radical which are generated during OH radical inititiated oxidation of alkenes. Some peroxy isomers can undergo intramolecular H atom abstraction followed by addition of oxygen molecule to form another peroxy radical. This two step process is termed as autoxidation. We are interested in directly measuring rates of autoxidation reactions using isomer specific near infrared spectroscopy of peroxy radicals.

Autoxidation reactions of peroxy radical generated from isoprene

Wennberg et al. Chem. Rev. 2018, 118, 3337-3390
Bianchi et al. Chem. Rev. 2019, 119, 3472-3509

Criegee Intermediate Chemistry: Alkene ozonolysis is an important process in the troposphere which leads to production of OH radicals and non-volatile organic compounds that can condense to form aerosol particles. Ozonolysis results in clevage of the alkene double bond producing Criegee intermediates and ketone products. In tropospheric conditions most of the Criegee intermediates decompose, however some fraction can be stabilized. These stabilized Criegee intermediates, SCI, have been recently shown to undergo bimolecular reactions with important traces molecules such as H2O, SO2 and RCOOH. However there is still significant uncertainity over yields of SCI particularly for larger biogenic SCI from ozonolysis of isoprene and terpenes. We are interested in directly measuring the SCI yields using novel scavengers and proton transfer mass spectrometry.

Criegee intermediates produced during ozonolysis of isoprene

Khan et al. Environ. Sci.: Processes Impacts, 2018, 20, 437-453
Nguyen et al. Phys. Chem. Chem. Phys. 2016, 18, 10241-10254

Funding Acknowledgement: The group gratefully acknowledges funding support provided by the Natural Environmental Research Council (NERC) and The Royal Society.

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