Synthesis of Novel Receptors From 7-Deoxycholic Acid and Studies on Their Cation Binding Properties

The synthesis and cation binding properties of chiral crown ethers derived from 7-deoxycholic acid along with their application in asymmetric Michael reaction are described.     

The quantitation of butyltin and cyclohexyltin compounds in the marine environment of British Columbia

A HPLC/GF AA procedure based on the use of C-18 columns is described for the quantitation of butyltin species in marine samples. When a mass spectrometer was used as detector (HPLC MS), evidence was obtained for the presence of other tin compounds in the samples. Extracts of samples were treated with CH₃MgBr and examined by using GC MS; the presence of Bu_nSnMe_4?n (n = 3–1, Bu = butyl) and Cy_nSnMe_4?n (n = 3,2, Cy = cyclohexyl) was confirmed in the derivatized seawater, bivalve flesh, and bivalve shell samples. Quantitative data are given for butyl- and cyclohexyl-tin species in seawater and the surface microlayer, and oyster flesh.     

Theoretical study of relative width of photonic band gap for the 3-D dielectric structure

Calculations for the relative width (Δω/ω₀) as a function of refractive index and relative radius of the photonic band gap for the fcc closed packed 3-D dielectric microstructure are reported and comparison of experimental observations and theoretical predictions are given. This work is useful for the understanding of photonic crystals and occurrence of the photonic band gap.     

Homoconjugation in the adamantane cage: DFT/IGLO studies of the 1, 3-dehydro-5-adamantyl cation, its isoelectronic boron analogue 1, 3-dehydro-5-boraadamantane, and related systems(1)(,)

The structure of 1,3-dehydro-5-adamantyl cation and its isoelectronic boron analogue 1,3-dehydro-5-boraadamantane as well as some related adamantane systems, hitherto unknown as persistent long-lived species, were investigated by using the density functional theory (DFT) method. (13)C and (11)B NMR chemical shifts of the compounds were also calculated using the IGLO method. Stabilization of the systems due to homoconjugation is discussed.     

SnCl4-catalyzed reaction of o-benzoquinones and aryl acetylenes: an unprecedented one-pot synthesis of tropone derivatives

Highly substituted tropone derivatives were obtained as a result of SnCl4-catalyzed cycloaddition of 3-methoxy-substituted o-benzoquinones with aryl acetylenes and subsequent rearrangement of the adducts with concomitant decarbonylation.     

High quality beam shaping by square soft-edge diaphragm combined with liquid crystal spatial light modulator

<正>The square soft-edge diaphragm with round angle is designed by Matlab,and is sent to a liquid crystal spatial light modulator by the computer.In order to obtain precompensation for the following laser system, local diaphragm transmission can be adjusted by feedback signals of surface-channel charge-coupled device (SCCD).This method can reduce the diffraction effect and realize no modulation,high stability,high homogeneity,and large scale laser beam.Several parameters of soft-edge diaphragms which affect the laser beam quality are studied systematically,and the optimized values are obtained.The method can avoid the serious modulation of hard edges and provide soft-edge diaphragms of different shapes in a fast and convenient way for the large scale laser beam system.     

Analysis of polyaromatic quinones in a complex environmental matrix using gas chromatography ion trap tandem mass spectrometry

GC/MS and GC/MS/MS in a quadrupole ion trap were used to analyze for anthraquinone, alkyl anthraquinones, benz[a]anthracene-7, 12-dione and 9-fluoranone in a sediment obtained from an aluminum smelter settling pond contaminated with polycyclic aromatic hydrocarbons. By standard GC/MS analysis many of these target compounds were either undetectable or their confirmation uncertain because of matrix interferences. Detection and identification were greatly improved by using GC/MS/MS. GC/MS/MS analyses were performed by selecting the molecular ion (M) of a target compound and fragmenting it via collision induced dissocation (CID) to yield product ions corresponding to loss of CO for unsubstituted compounds or CO plus CH(3) for alkylated compounds. The CID conditions were optimized using anthraquinone and 2-methylanthraquinone standards by varying the CID excitation energy and RF storage levels to yield optimum amounts of fragment ions. CID experiments were performed using both resonant and non-resonant wave forms. Although both excitation techniques gave comparable results for the removal of matrix interferences, non-resonant excitation provided more characteristic spectra for the alkylated anthraquinones. Monitoring of secondary fragmentation products, such as M-2CO, provided greater discrimination from matrix interferences than the use of primary fragmentation products, such as M-CO.     

The use of High-Performance Liquid Chromatography for the Speciation of Organotin Compounds

This review of the use of high-performance liquid chromatography (HPLC) for the speciation of organotin compounds which are primarily of significance in the marine environment is divided into sections on the basis of the different HPLC modes of separation. However, it should be noted that such a classification does not exist in reality. For instance, in an ion-pair reversed-phase system the separation mechanism for the ionic solutes may be ion-pair partitioning, or ion exchange, or both. The relevant practical information (e.g. column type, mobile phase, method of detection and detection limit) is presented in tabular form. A brief overview of the reported detection methods is included, because the delay in development of an easily interfaced, specific and sensitive detector has hindered the use of HPLC for organotin speciation studies. The literature reviewed covers publications from 1977, the year of the first application of HPLC to organotin speciation, to April 1995.     

From crystal to crystal: A reconstructive solid-state reaction

The crystal structure of the Lewis acid-base adduct of 2-chloro-2-boraindane and diethylether was determined by X-ray diffraction. After abstraction of the boron-coordinated Et₂O molecule in vacuo, the crystal and molecular structure of the solvent-free boraindane, earlier synthesized by Kaufmann and Schacht [1], was studied on the resulting crystalline material. The different crystal packing in both structures and a diffraction experiment on an oriented single crystal showed that the reaction is reconstructive and that a rearrangement of the molecules parallels the change in molecular geometry.     

Mass spectra of 6-aza and 11-aza steroids

A study on the behavior of a considerable number of 6-aza and 11-aza steroids in the mass spectrometer is recorded and discussed. The results illustrate that the hetero atom has a precominant effect in directing the fragmentation of these substances, and interesting differences from the normal steroid fragmentation patterns are therefore observed.