Chemical Kinetic Study of the Reaction of CH2OO with CH3O2

Criegee intermediates play an important role in the oxidizing capacity of the Earth's troposphere. Although their reactivity has been studied extensively in the past, their reactions with radical species remain underexplored. We have investigated the reaction of the simplest Criegee intermediate, CH2OO, with the methyl peroxy radical, CH3O2, as a model system to explore the reactivity between Criegee intermediates and peroxy radicals. Using a multipass UV-Vis spectrometer coupled to a pulsed-laser photolysis flow reactor, CH2OO and CH3O2 were generated simultaneously from the photolysis of CH2I2/CH3I/O2/N2 mixtures with CH2OO measured directly near 340nm. We determined a reaction rate coefficient kCH2OO+CH3O2 = (1.6 ± 0.5)1011 cm3 s1 at 294 K and 10 Torr, where the influence of iodine adducts is reduced. This rate coefficient is faster than previous theoretical predictions, highlighting the challenges in accurately describing the interaction between zwitterionic and bi-radical characteristics of Criegee intermediates.