Chemistry of O-Benzoquinones and Masked O-Benzoquinones IV. Synthesis of O-Spirodienonelactones from Unsymmetric Catechols

We describe the syntheses of 6, 8-di-tert-butyl-, 7, 9-di-tert-butyl., 6,7-di-n-propyl and 8, 9-di-n-propyl-O-spirodienonelactone from 3, 5-di-tert-butylcatechol and 3, 4-di-n-propylcatechol.     

Effect of evaporation temperature on the formation of particulate membranes from crystalline polymers by dry-cast process

The membrane formation of crystalline poly(ethylene-co-vinyl alcohol) (EVAL), poly(vinylidene fluoride) (PVDF), and polyamide (Nylon-66) membranes prepared by dry-cast process was studied. Membrane morphologies from crystalline polymers were found to be strongly dependent on the evaporation temperature. At low temperatures, all the casting solution evaporated into a particulate morphology that was governed by the polymer crystallization mechanism. The rise in the evaporation temperature changed EVAL membrane structure from a particulate to a dense morphology. However, as the temperature increased PVDF and Nylon-66 membranes still exhibited particulate morphologies. The membrane structures obtained were discussed in terms of the characteristics of polymer crystallization in the casting solution theoretically. At elevated temperatures the crystallization was restricted for the EVAL membrane because the increase rate in the polymer concentration was fast relative to the time necessary for growth of nuclei. Nonetheless, the time available for PVDF and Nylon-66 with stronger crystalline properties was large enough to form the crystallization-controlled particulate structure that differed in particle size only. In addition, particles in the PVDF membrane were driven together to disappear the boundary, but those in the Nylon-66 membrane exhibited features of linear grain boundary. The difference in particle morphology was attributed to the Nylon-66 with the most strongly crystalline property. Therefore, the kinetic difference in the crystallization rate of the polymer solution play an important role in dominating the membrane structure by dry-cast process.     

Hair as an indicator of environmental exposure in Hong Kong

Eleven human hair samples were taken from the Chinese residents of Hong Kong for the study of hair trace elemental level and environmental exposures. Absolute neutron activation analysis and Ge(Li) gamma-ray spectrometry were applied in the determination of the trace elemental level. All results are reported in parts per million except for sulfur and oxygen which are reported in percent. The trace element content of hair from a drug addict was found to be considerably different from other sampled people. Comparison of the normal concentrations of the trace elements of the Chinese residents of Hong Kong was made with those from people of various other national, socio-cultural and environmental backgrounds. It was found that together with a few other trace elements, Ni, Sr, Zr and Hg content of the Chinese Residents of Hong Kong show a higher level than those of the other sampled people.     

胆酸钠与支撑磷脂双层膜作用的电化学研究

采用电化学方法研究胆酸钠(NaC)与s-BLM的相互作用, 并结合实验结果对NaC与s-BLM的作用机理进行了讨论.     

Temperature dependence of CO insertion on S-, Ag-, and Cu-promoted Rh/SiO2 catalysts

The addition of sulfur and silver to Rh/SiO₂ inhibits hydrogenation of C₂H₄, but promotes CO insertion and extends the linearity of Arrhenius curves for CO insertion above 543 K.

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Rh/SiO₂ C₂H₄, CO CO 543 .

     

Immunochemical determination of dioxins in sediment and serum samples

Polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) are considered highly toxic contaminants and the environmental and biological monitoring of these compounds is of great concern. Immunoassays may be used as screening methods to satisfy the growing demand for rapid and low cost analysis. In this work, we describe the application of an immunoassay that uses 2,3,7-trichloro-8-methyldibenzo-p-dioxin (TMDD) as a surrogate standard for 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) to sediment and human serum samples. Sample extraction and preparation methods were developed with the aim to establish the simplest, cost-effective and efficient removal of the matrix interferences in the enzyme-linked immunosorbent assay (ELISA). The overall method for sediments is based on a hexane extraction; clean up by a multilayered silica gel column and an activated carbon column; an organic solvent exchange with DMSO–Triton X-100 and ELISA measurement. The gas chromatography–high resolution mass spectrometry (GC–HRMS) validation studies (n = 13) revealed that the method is suitable for the toxic equivalents (TEQ) screening of dioxin in sediments with a method detection limit of about 100 pg g⁻¹ dry sediment with a precision of 13–33% R.S.D. The analysis of a large number of samples originating from different sources would be required to establish more precisely the screening level, as well as the number of false positives and negatives of dioxin TEQ by the immunoassay for sediments. The immunoassay method for sediment analysis offers improvement in speed, sample throughput, and cost in comparison to GC–HRMS. Dioxins were determined in serum samples after a simple liquid–liquid extraction and solvent exchange into DMSO–Triton X-100 without further dilution. The current method (approximate method LOQ of 200 pg ml⁻¹ serum) is not sufficiently sensitive for the determination of dioxins in serum to measure acceptable exposure limit.     

The Studies of Free Radical Cyclization Reactions Mediated by Sulfonyl Chloride (II)

A study on the free radical cyclization reaction of substituted 1,6-dienes mediated by p-toluenesulfonyl chloride is described.     

CO disproportionation on Ni-based catalysts

Ni/SiO₂ exhibits higher activity for CO dissociation than coprecipitated Na–Mn–Ni, which is a higher oxygenate synthesis catalyst at 303 K, while Na–Mn–Ni exhibited higher CO dissociation activities at 673 K.     

Free Radical Reaction between 1,6-Dienes and P-Toluenesulfonyl Cyanlde

A sulfonyl-radical-induced addition-cyclization reaction of 1,6-dienes with p-toluenesulfonyl cyanide giving functionalized cyclopentane systems is described.