The kinetics of the acetonylperoxy/hydroperoxy cross-reaction has been studied using the Infrared Kinetic Spectroscopy technique at atmospherically relevant temperatures. In this technique, precursor molecules are converted via excimer laser flash photolysis into HO2 and CH3C(O)CH2O2 which are then monitored in the infrared by diode-laser/wavelength-modulation detection and ultraviolet absorption at 300 nm, respectively. Simultaneous fitting of the kinetics of the resulting decay curves was used to obtain the rate constant for the acetonylperoxy/hydroperoxy reaction. This analysis also permitted the determination of dependence of the hydroperoxyself-reaction on the acetone concentration due to formation of a hydrogen-bonded complex between hydroperoxy and acetone. This chaperone mechanism enhances the rate of the self-reaction via the following reactions: HO2 + (CH3)2CO → (CH3)2CO●HO2 (1) (CH3)2CO●HO2 + HO2 → H2O2 + O2 + (CH3)2CO (2) which must be included in laboratory study of these systems. The rate constant for the acetonylperoxy/hydroperoxy reaction at room temperature was determined to be (2.9 ± .53) x 10-12 cm3 molecules-1 s-1. In addition, the chaperone mechanism was found to enhance the self-reaction significantly even at room temperature. The study of these reactions has been repeated at temperatures between 220 K and 280 K. This determination allows for an understanding of kinetics involving these species occurring in the troposphere.

Determination of rate constants for acetonylperoxy/hydroperoxy self reactions and cross reaction via infrared kinetic spectroscopy

253rd National Meeting (2017)

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