Functionalized Hydroperoxide Formation from the Reaction of Isoprene-Derived Criegee Intermediates with Formic Acid: Experiment and Theory

摘要: Isoprene is the most abundant non-methane hydrocarbon emitted into Earths atmosphere. Ozonolysis is an atmospheric sink for unsaturated hydrocarbons and generates carbonyl oxide zwitterions (R1R2C= O+ O) known as Criegee intermediates (CIs). Ozonolysis of isoprene produces three CIs, including two four-carbon unsaturated CIs: methyl vinyl ketone oxide (MVK-oxide) and methacrolein oxide (MACR-oxide) that differ only by the position of a methyl group. We explore the impact of this structural difference on the reactivity of MVK-oxide and MACR-oxide via their reactions with formic acid. Using multiplexed photoionization mass spectrometry, we find that both reactions lead to the formation of low-volatility functionalized hydroperoxide products species that have been implicated in the formation of secondary organic aerosols. High-level theoretical calculations demonstrate that the products from both …