Atmospheric oxidation mechanism of acenaphthene initiated by OH radicals

Atmospheric Chemistry of Allylic Radicals from Isoprene: A Successive Cyclization-Driven Autoxidation Mechanism

“…Therefore, the H-shift-driven autoxidation pathway could not be significant for the transformation of RO 2 • from the allylic radicals, unlike RO 2 • from the addition intermediates of isoprene reactions. , Based on the unsaturated character of the formed RO 2 • from allylic radicals, they have a probability of reacting via a cyclization reaction from the terminal O-atom attacking unsaturated bonds. In fact, previous studies found that the cyclization reaction can favorably occur in unsaturated RO 2 • formed from the •OH addition intermediates of unsaturated organic compounds such as isoprene, α-pinene, β-pinene, benzene, alkyl-substituted benzene (such as toluene and trimethylbenzene), xylene ( o -, x -), phenol, and H-abstraction intermediates of unsaturated C 3 H 6 and C 4 H 8 . ,− The feasibility of the cyclization reaction of unsaturated RO 2 • highly depends on the exact structure of the unsaturated RO 2 • , e.g., the cyclization reaction plays an important role in the transformation of RO 2 • from • OH addition intermediates of benzene, but not for naphthalene and alkyl-substituted naphthalene. ,− It deserves mentioning that the investigated systems for the cyclization reaction only include the unsaturated RO 2 • from aromatic hydrocarbons and nonaromatic hydrocarbons with one unsaturated bond. Structurally, RO 2 • from allylic radicals is significantly different from the investigated ones since it includes two conjugate unsaturated bonds.…”

“…Reactants and transition states may have multiple conformers. Previous studies found that the involvement of multiconformers can more precisely predict the reaction kinetics, compared to single-conformer approximation. ,,,− A so-called single-conformer approximation implies that only one conformer for reactant and transition state was used in studying reaction mechanism and kinetics. − ,,,,,− ,− Here, multiconformer approximation was considered in the crucial reaction steps. The crucial reaction steps are determined by a kinetics analysis based on single-conformer approximation (details in the SI).…”

Enigma of Urban Gaseous Oxygenated Organic Molecules: Precursor Type, Role of NOx, and Degree of Oxygenation

“…In total, around 1000 OOM species were identified. Some species, such as isoprene-derived OOMs (Table S1), nitrophenols (Table S2), and contamination-related compounds (Table S3), were identified based on the peak list established in previous studies. , It should be noted that, besides contamination-related compounds, nitrophenols were also not included in the calculation of OOM concentration, despite their high signals in the mass spectra owing to their high sensitivity in nitrate-CIMS. , Although nitrophenols are also mainly formed from aromatic VOCs, their formation , does not involve autoxidation that is central to the OOM formation. In addition, nitrophenols have relatively high volatility , and their contribution to SOA is limited and still certain uncertainties exist .…”

“…55,56 It should be noted that, besides contamination-related compounds, nitrophenols were also not included in the calculation of OOM concentration, despite their high signals in the mass spectra owing to their high sensitivity in nitrate-CIMS. 57,58 Although nitrophenols are also mainly formed from aromatic VOCs, their formation 59,60 does not involve autoxidation that is central to the OOM formation. In addition, nitrophenols have relatively high volatility 61,62 and their contribution to SOA is limited and still certain uncertainties exist.…”

Prediction of •OH-Initiated and •NO3-Initiated Transformation Products of Polycyclic Aromatic Hydrocarbons by Electronic Structure Approaches

“…C5 is predicted to be the most reactive site of ACE, which is consistent with the observed 5-nitroacenaphthene as the major product resulting from the • OH-initiated reaction of ACE. 75,76 4-Nitroacenaphthene identified as the major product formed from the N 2 O 5 +ACE reaction was not expected to the significant ambient product since • NO 3 totally dominates over N 2 O 5 under ambient atmospheric conditions. The major mono-NPAH products of BKF and FLT (7-nitrobenzo[k]fluoranthene 62 and 2-nitrofluoranthene 73 ) also support the prediction results that the C7 atom of BKF and the C3 atom of FLT are the most reactive, respectively.…”