June 12, 2015
Journal Article

Mechanism of the hydroxy radical oxidation of methacryoyl peroxynitrate (MPAN) and its pathway toward secondary organic aerosol formation in the atmosphere

Abstract

Methacryoyl peroxynitrate (MPAN), the acylperoxyl nitrate of methacrolein, has been suggested to be an important secondary organic aerosol (SOA) precursor from isoprene oxidation. Yet, the mechanism by which MPAN produces SOA via reaction with the hydroxyl radical (OH) is unclear. We systematically evaluate three proposed mechanisms in controlled chamber experiments and provide the first experimental support for the theoretically-predicted lactone formation pathway from the MPAN + OH reaction, producing hydroxymethyl-methyl-a-lactone (HMML). The decomposition of the MPAN-OH adduct yields HMML + NO3 (~ 75%) and hydroxyacetone + CO + NO3 (~ 25%), out-competing its reaction with atmospheric oxygen. The production of other proposed SOA precursors, e.g., methacrylic acid epoxide (MAE), from MPAN and methacrolein are negligible (

Revised: July 28, 2015 | Published: June 12, 2015

Citation

Nguyen T.B., K.H. Bates, J.D. Crounse, R.H. Schwantes, X. Zhang, H.G. Kjaergaard, and J.D. Surratt, et al. 2015. Mechanism of the hydroxy radical oxidation of methacryoyl peroxynitrate (MPAN) and its pathway toward secondary organic aerosol formation in the atmosphere. Physical Chemistry Chemical Physics 17, no. 27:17914-17926. PNNL-SA-109565. doi:10.1039/c5cp02001h