13177-29-2Relevant articles and documents
Effect of aerosol chemical composition on the photodegradation of nitro- polycyclic aromatic hydrocarbons
Feilberg, Anders,Nielsen, Torben
, p. 789 - 797 (2000)
The photodegradation of four ring nitro-PAHs in the presence of organic aerosol constituents has been investigated in model systems to determine their degradation mechanism under ambient air conditions. Light-induced radical chain reactions initiated by organic aerosol constituents, e.g., oxy- PAHs, is most likely to be the dominant degradation pathway for particle- associated nitro-PAH. The photodegradation rates were investigated in a chemical model system simulating the liquid film on particles from diesel exhaust and wood stove stack gases. Relative rates were obtained in pure solutions (direct photolysis) and in the presence of different classes of organic aerosol components comprising PAHs, hydroxy-PAHs, substituted phenols, benzaldehydes, and oxy-PAHs (including polycyclic aromatic quinones) (indirect photolysis). Members of the four latter compound classes are demonstrated to accelerate the photodegradation rate. The mechanisms proposed to explain these effects include both radical chain reactions and photoinduced hydrogen abstraction by nitro-PAHs. PAHs that are known sensitizers of singlet O2 did not accelerate the decay. Certain oxy-PAHs strongly accelerate the nitro-PAH decay, whereas others have no effect. This difference is related to the nature of the excited state of the oxy-PAH and the ability to initiate radical chain reactions. The relevance of the model system and the environmental implications of the results are discussed, and the results are compared with relative degradation rates from smog chamber studies with the same compounds. The photodegradation of four ring nitro-PAHs in the presence of organic aerosol constituents has been investigated in model systems to determine their degradation mechanism under ambient air conditions. Light-induced radical chain reactions initiated by organic aerosol constituents, e.g., oxy-PAHs, is most likely to be the dominant degradation pathway for particle-associated nitro-PAH. The photodegradation rates were investigated in a chemical model system simulating the liquid film on particles from diesel exhaust and wood stove stack gases. Relative rates were obtained in pure solutions (direct photolysis) and in the presence of different classes of organic aerosol components comprising PAHs, hydroxy-PAHs, substituted phenols, benzaldehydes, and oxy-PAHs (including polycyclic aromatic quinones) (indirect photolysis). Members of the four latter compound classes are demonstrated to accelerate the photodegradation rate. The mechanisms proposed to explain these effects include both radical chain reactions and photoinduced hydrogen abstraction by nitro-PAHs. PAHs that are known sensitizers of singlet O2 did not accelerate the decay. Certain oxy-PAHs strongly accelerate the nitro-PAH decay, whereas others have no effect. This difference is related to the nature of the excited state of the oxy-PAH and the ability to initiate radical chain reactions. The relevance of the model system and the environmental implications of the results are discussed, and the results are compared with relative degradation rates from smog chamber studies with the same compounds.
Photochemical Nitration by Tetranitromethane. VIII. Isolation, X-Ray Structural Analysis and Chemical Properties of a Vicinal Nitro/trinitromethyl Adduct from Fluoranthene
Eberson, Lennart,Hartshorn, Michael P.,Radner, Finn,Robinson, Ward
, p. 410 - 415 (2007/10/02)
The photolysis of a dichloromethane solution of fluoranthene and tetranitromethane by light with cut-off at λ less than 435 nm gave a mixture of nitro/trinitromethyl adducts (ca. 10percent) and nitrofluoranthenes (ca. 60percent).One of the adducts could be isolated and proved to be a vicinal one trans-2-nitro-3-trinitromethyl-2,3-dihydrofluoranthene (1), as demonstrated by in X-ray crystallographic analysis.Adducts were formed in acetonitrile too, but the adduct yield was smaller.Adduct 1 was stable for many days in dichloromethane but slowly (τ1/2 about 19 h) eliminated nitroform to give 2-nitrofluoranthene in acetonitrile, whereas added hindered or unhindered bases strongly accelerated the reaction in both dichloromethane and acetonitrile.Under GLC condition 1 analyzed as 2-nitrofluoranthene.The spin adduct of trinitromethyl radical and α-phenyl-N-tert-butylnitrone (PBN) was formed and detected by EPR spectroscopy in low concentration and persisted for a long time when 1 and PBN were kept in dichloromethane solution.
A dichotomy in the nitration of fluoranthene with NO2/N2O4: Mechanistic and toxicological implications
Squadrito,Fronczek,Church,Pryor
, p. 2616 - 2621 (2007/10/02)
The nitration of fluoranthene with nitrogen dioxide can occur by two distinctive reaction pathways. These paths can be distinguished by product analysis, since fluoranthene is a nonalternant hydrocarbon. Free-radical nitration and electrophilic nitration give different products. In solvents with dielectric constants lower than that of CH2Cl2 and in the absence of acid catalysis, the exclusive reaction pathway is homolytic in nature. The products of the homolytic reaction pathway can be interpreted as arising via a multiple-step addition-elimination mechanism and are notable for the formation of 2-nitrofluoranthene (the major product in CCl4 but absent under electrophilic nitration conditions) and the unusually large amounts of the expected 1,2-dinitrofluoranthene and 1,3-dinitrofluoranthene. The ionic reaction pathway is subject to both Lewis and Bronsted acid catalysis, particularly in CH2Cl2, and is inhibited by nonnucleophilic bases like 2, 6-di-tert-butylpyridine. At temperatures lower than 25°C, the ionic reaction pathway predominates, even in CCl4. 2-Nitrofluoranthene is a marker for the free-radical nitration of fluoranthene, and its presence in polluted tropospheric air suggests that free-radical nitration by NO2 may occur under atmospheric conditions.
