Advances in Computational Simulation of Autoxidation Reactions of Atmospheric Peroxyalkyl Radicals

• • RO2· autoxidation proceeds via intramolecular H-shift and subsequent O2 addition, with rate constants often exceeding 1 s−1 for fast H-shift reactions, enabling competition with bimolecular reactions at NO concentrations below ~10 ppt, thereby enhancing HOM yields and SOA formation. • • For alkane-derived RO2·, 1,5-H-shift reactions are typically favored with energy barriers around 15–20 kcal/mol, but functional groups such as carbonyl or hydroxyl can lower barriers by up to 5 kcal/mol, accelerating autoxidation and increasing HOM production by up to an order of magnitude. • • In aromatic-derived RO2·, the presence of a double bond in the ring facilitates fast intramolecular reactions, with rate constants up to 10^3 s−1, leading to rapid formation of highly oxygenated products that contribute to SOA, as observed in limonene oxidation studies. • • Heteroatom-containing RO2· (e.g., N, S) exhibit distinct autoxidation pathways; for example, nitrate-substituted RO2· can undergo H-shift with barriers as low as 10 kcal/mol, significantly altering the product distribution and potentially increasing SOA yields by 20–30% under low-NO conditions.