Nitro-PAHs are globally worrisome air pollutants because their high direct-acting mutagenicity and carcinogenicity. A mechanistic understanding of their formation is of crucial importance for successful prevention of their atmospheric pollution. Here, the formation of nitroPAHs arising from the OH-initiated and NO 3 -initiated atmospheric reactions of PAHs was investigated by using quantum chemical calculations. It is widely assumed that OH or NO 3 radicals attack on the C atoms of the aromatic rings in the PAH molecule, followed by the addition of NO 2 to the OH−PAH or NO 3 −PAH adducts at the ortho position and the loss of water or nitric acid to form nitro-PAHs. However, calculations show that the direct loss of water from the OH−NO 2 −PAH adducts via the unimolecular decomposition is energetically unfavorable. This study reveals for the first time that water molecule plays an important catalytic effect on the loss of water from the OH−NO 2 −PAH adducts and promotes the formation of nitro-PAHs. In addition, the introduction of water unwraps new formation pathway through the addition of NO 2 to the OH−PAH or NO 3 −PAH adduct at the para position. The individual and overall rate constants for the addition reactions of PAHs with OH and NO 3 radicals were deduced by using the Rice−Ramsperger−Kassel−Marcus (RRKM) theory.

[structure: see text] Bulky phenanthracenyl imidazolium-derived carbene ligands were investigated for copper-free Sonogashira coupling with terminal acetylenes. Aryl bromides and iodides gave coupled products in excellent yields from the Pd(PPh(3))(2)Cl(2) complex with potassium t-butoxide and 18-crown-6 in THF. A remarkable dependence on the size of the ligand was found. The highest yields were obtained with the bulky 2,9-dicyclohexyl-10-phenanthryl ligand 5.

Due to rapid urbanization and the implementation of ecological civilization construction in China, many industrial factories have been closed or relocated. Therefore, numbers of contaminated sites were generated with contaminated soils which may pose a risk to receptors living nearby. This study presented a spatial health risk assessment and hierarchical risk management policy making for mercury (Hg) in soils from a typical contaminated site in the Hunan Province, central China. Compared with the second class value (0.3 mg/kg) of the Chinese Environmental Quality Standard for Soils, the mean concentrations of Hg in the three soil depths exceeded the second class value. The non-carcinogenic risk of Hg probably posed adverse health effects in 41, 30 and 36 % of the surface soil, the moderate soil and subsoil, respectively, under a sensitive land scenario. The non-carcinogenic risk temporarily posed no adverse health effects in most areas under an insensitive land scenario except for the area around sampling site S29. Spatially, the central, southwest and northeast parts of the contaminated land under a sensitive land scenario should be regarded as the priority regions. For non-carcinogenic effects, the exposure pathways that resulted in the higher levels of exposure risk were ingestion and inhalation of vapors, followed by dermal contact and inhalation of particles. A risk-based integrated risk management policy including the hierarchical risk control values for different soil depths and the calculated remediation earthwork was proposed with consideration of the cost-benefit effect for the related decision-makers.

[reaction: see text] A highly efficient catalytic borylation process with aryldiazonium ions was developed using a carbene-palladium catalyst formed in situ to give arylpinacolatoborane products. An X-ray structure for the N-heterocyclic carbene-palladium complex, used as the catalyst formed from bis(2,6-diisopropylphenyl)-4,5-dihydroimidazolium chloride, was obtained without added base.