Mechanism and Kinetics of the Initial Oxidative Ring-Opening of Corannulene Radicals under Combustion Conditions

Black carbon emissions significantly impact air pollution and global warming, yet the oxidation mechanisms of curved polycyclic aromatic hydrocarbons (PAHs), which are more reactive than planar ones, remain poorly understood. In this study, the oxidation and initial ring-opening mechanisms of the corannulene radical (Cor·), the smallest stable curved PAH, were systematically investigated using ReaxFF molecular dynamics (MD), density functional theory (DFT) with ONIOM methods, and Master Equation System Solver (MESS). MD simulations reveal that the degradation is predominantly driven by the radical addition of O₂ at the radical site (64% probability), forming the corannulene peroxyl radical (CorOO·). Subsequent unimolecular transformation analysis shows that oxygen atom transfer pathways are kinetically favored over hydrogen atom transfer and oxygen atom dissociation. Specifically, the R3-1 pathway, characterized by the lowest energy barrier (-7.8 kcal/mol), emerges as the primary sink for CorOO·, leading to efficient CO elimination. Rate constant calculations (500-2000 K) further confirm that cyclization-initiated fragmentation governs the initial oxidative degradation. This work provides the first detailed microscopic kinetic description of curved PAH oxidation, bridging the gap between planar PAH degradation and fullerene formation in combustion models.