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An organic tracer method, recently proposed for estimating individual contributions of toluene and α-pinene to secondary organic aerosol (SOA) formation, was evaluated by conducting a laboratory study where a binary hydrocarbon mixture, containing the anthropogenic aromatic hydrocarbon,toluene, and the biogenic monoterpene, α-pinene, was irradiated in air in the presence of NOx to form SOA. The contributions of toluene and α-pinene to the total SOA concentration, calculated using the organic tracer method, were compared with those obtained with a more direct 14C content method. In the study, SOA to SOC ratios of 2.07 ± 0.08 and 1.41 ± 0.04 were measured for toluene and α-pinene SOA, respectively. The individual tracer-based SOA contributions of 156 µg m-3 for toluene and 198 µg m-3 for α-pinene, which together accounted for 82% of the gravimetrically determined total SOA concentration, compared well with the 14C values of 182 and 230 µg m-3 measured for the respective SOA precursors. While there are uncertainties associated with the organic tracer method, largely due to the chemical complexity of SOA forming chemical mechanisms, the results of this study suggest the organic tracer method may serve as a useful tool for determining whether a precursor hydrocarbon is a major SOA contributor. [ABSTRACT FROM AUTHOR]

The article provides insights in structural biology and chemistry of the terpenoid cyclases. Terpenoid cyclases catalyze the most complex chemical reactions occuring in the environment. They generate a unique hydrocarbon product with remarkable structural and stereochemical precision. The article also discusses monototerpene cyclases, diterpene cyclases, triterpene cyclases and antibody catalysis of cationic cyclization reactions.

A new and efficient synthesis of a variety of highly embellished bicyclooctenones having an endo- vinyl moiety and their sigmatropic shifts in ground and excited states leading to a stereoselective route to substituted cis-decalins and diquinane frameworks have been described. Functionalized bicyclo[2.2.2]octenones having an endo-vinyl group and a β,γ-enone chromophore were prepared by in situ generation of 6-chloromethyl-6-hydroxycyclohexadienones and cycloaddition with butadiene (also generated in situ) followed by manipulation of the adducts. The presence of contiguous carbonyl, hydroxyl, and chloromethyl groups in adducts led to the introduction of various alkyl groups α to the ketone in a stereoselective fashion. The 3,3-sigmatropic shift in the bridged bicyclic compounds gave the corresponding cis-decalins, whereas the triplet sensitized irradiation led to the formation of diquinanes as a result of a 1,2-acyl shift. [ABSTRACT FROM AUTHOR]