Autoxidation Mechanism and Kinetics of Methacrolein in the Atmosphere

Elucidating the autoxidation of volatile organic compounds (VOCs) is crucial to understanding the formation mechanism of secondary organic aerosols, but it has been proven to be challenging due to the complexity of reactions under atmospheric conditions. Here, we report a comprehensive theoretical study of atmospheric autoxidation in VOCs exemplified by the atmospherically important methacrolein (MACR), a major oxidation product of isoprene. The results indicate that the Cladducts and H-abstraction products of MACR readily react with O2 and undergo subsequent isomerizations via H-shift and cyclization, forming a large variety of lowly and highly oxygenated organic molecules. In particular, the first-and third-generation oxidation products derived from the Cl-adducts and the methyl-H abstraction complexes are dominated in the atmospheric autoxidation, for which the fractional yields are remarkably affected by the NO concentration. The present findings have important implications for a systematical understanding of the oxidation processes of isoprene-derived compounds in the atmospheric environments.

Automated summary

In this study, the autoxidation of volatile organic compounds (VOCs) in the atmosphere was theoretically investigated using methacrolein (MACR) as the example. The results revealed that MACR's Cladducts and H-abstraction products react with O2 and undergo isomerizations via H-shift and cyclization, leading to the formation of a diverse range of lowly and highly oxygenated organic molecules. Furthermore, the first and third-generation oxidation products derived from the Cl-adducts and the methyl-H abstraction complexes dominate the atmospheric autoxidation, with their yields significantly influenced by NO concentration. These findings are of great importance for a systematic understanding of the oxidation processes of isoprene-derived compounds in atmospheric environments.