No abstract

Chlorinated paraffins (CPs) are industrially produced in large quantities in the Liaohe River Basin. Their discharge inevitably causes environmental contamination. However, very limited information is available on their environmental levels and distributions in this typical industrial region. In this study, short chain CPs (SCCPs) were analyzed in sediments, paddy soils, and upland soils from the Liaohe River Basin, with concentrations ranging from 39.8 to 480.3 ng/g dry weight. A decreasing trend in SCCP concentrations was found with increasing distance from the cities, suggesting that local industrial activity was the major source of SCCP contamination. A preliminary sediment inventory of SCCPs indicated approximately 30.82 tonnes of SCCPs residual in the sediments from the Liaohe River. The average discharge of SCCPs was estimated to be about 74.4 mg/tonne industrial wastewater. The congener group profiles showed that the relative abundances of shorter chain and lower chlorinated CP congeners (C 10 −CPs with 5 or 6 chlorine atoms) in soils in rural areas were higher than in sites near cities, which demonstrated that long-range atmospheric transportation could be the major transport pathway. Environmental degradation of SCCPs might occur, where higher chlorinated congeners could dechlorinate to form the lower chlorinated congeners.

Hydrometalation of acetylenes illustrated in eq 1 is a superior method for preparing stereodefined alkenylmetal species, which are particularly useful for the construction of olefinic linkages with predictable stereochemistry. Hydrometalation reactions1 including hydroboration,18 -alumination,lb -magnesation,lc -silylation,ld -stannation,18 and -zirconation,lf etc., have been routinely utilized in the synthesis of complex natural products. Herein we report a new entry to this series of reactions, namely the first hydrozincation of acetylenes, and demonstrate its application to further synthetic transformations.Recently, organozinc compounds of the type RZnX (R = alkyl; X = halogen, R, etc.) have been widely recognized as versatile carbon nucleophiles in organic synthesis owing to their selective reactivities.2 Alkenylzinc compounds are usually prepared via transmetalation of appropriate organometallic reagents, typically organolithium, -magnesium, or -boron compounds, with zinc salts or diethylzinc.2a-C|3 Direct reductive metalation of alkenyl halides with zinc metal can also be effected, but the stereochemical integrity of the starting alkenyl halide is not always retained in the zinc reagent.4 If hydrozincation of acetylenes (eq 1, "M-H" = "ZnHX") could be executed in a stereoselective manner, this reaction could become a straightforward method to prepare stereochemically defined alkenylzinc reagents. While hy-