Etudes sur la nature des «pinks» par thermogravimétrie et spectrograpnie infrarouge. I

Résumé L'étude thermogravimétrique des 2 réactions à l'état solide SnCl₂+ +CrO₃ et SnCl₂+K₂Cr₂O₇ pour différentes proportions des constituants, montre que le «pink» formé pour un rapport Sn/Cr supérieur à 5 n'est pas une combinaison de chrome et d'étain.Le spectre d'absorption infrarouge de la poudre violette recueillie à partir de 600 ne présente aucune bande d'absorption en dehors de celles de SnO₂ et de Cr₂O₃. Il s'agit essentiellement d'oxyde d'étain dans lequel se trouve finement dispersé de 2 à 8% d'oxyde Cr₂O₃.

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Summary The thermogravimetric study of two reactions in the solid state, namely SnCl₂+CrO₃ and SnCl₂+ K₂Cr₂O₇ with different proportions of the reactants show that the pink produced by a ratio of Sn/Cr above 5 is not a compound of chromium and tin.The infra red absorption spectrum of the violet powder collected from 600 on shows no absorption band except those of SnO₂ and Cr₂O₃. We are dealing here essentially with a tin oxide containing 2 to 8% of finely dispersed oxide Cr₂O₃.

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Zusammenfassung Die thermogravimetrische Untersuchung der beiden Festkörperreaktionen zwischen Zinn(II)-chlorid und Chromsäureanhydrid bzw. Zinn(II)-ohlorid und Kaliumbichromat bei verschiedenen Gewichtsverhältnissen ergab, daß das bei einem Sn/Cr-Verhältnis > 5 entstehende Pink keine Verbindung aus Chrom und Zinn ist.Das IR-Absorptionsspektrum des über 600 erhaltenen violetten Pulvers enthält keinerlei Absorptionsbande außer denen des SnO₂ und des Cr₂O₃. Es handelt sich im wesentlichen um Zinnoxyd, in dem sich 2 bis 8% Cr₂O₃ in feiner Verteilung finden.

     

Comprehensive two-dimensional liquid chromatography and hyphenated liquid chromatography to study the degradation of poly(bisphenol A)carbonate

Size exclusion chromatography (SEC), gradient polymer elution chromatography (GPEC) and liquid chromatography at critical conditions (LC-CC) have been developed and applied to observe chemical changes in poly(bisphenol A)carbonate (PC) due to hydrolytic degradation. Especially LC-CC appeared to be very successful to observe differences in functionality of PC as result of hydrolytic degradation. Observed differences due to degradation could be identified by (semi) on-line coupling to matrix assisted laser desorption-ionization time-of-flight mass spectrometry (MALDI-TOF-MS). The differences in functionality could be attributed to the formation of different end-groups, i.e. OH end-groups. In addition, comprehensive two-dimensional liquid chromatography (2D-LC) has been applied successfully to study the hydrolytic degradation of PC. LC-CC x SEC showed that the formation of PC with different end-groups occurred over the whole molecular mass range. This information could not be obtained with the separate liquid chromatographic techniques, thereby illustrating the added value of 2D-LC.     

Gas chromatography-mass spectrometry analysis of alkylphenols in cod (Gadus morhua) tissues as pentafluorobenzoate derivatives

A highly selective and sensitive method for the determination of 30 meta- and para-substituted alkylphenols from phenol (C0) to nonylphenol (C9) in biota is described. Dichloromethane extracts of spiked cod liver and muscle samples are cleaned up by gel permeation chromatography, derivatised with pentafluorobenzoyl chloride and analysed by gas chromatography-mass spectrometry with negative-ion chemical ionisation. Quantification is done with isotope dilution of five internal standards of different chain length. The detection limits were in the low microg/kg levels. There were encountered problems with background levels of 4-nonylphenol. 4-Nonylphenol isomers were found in a number of plastic and rubber products used in the laboratory.     

Twin comprehensive two-dimensional gas chromatographic system: concept and applications

A twin GC x GC system has been designed which enables the analysis of a sample by means of two different and independent column combinations simultaneously. Both combinations are incorporated in the same oven, using the same temperature programme, and are fed using a 50:50 column-entrance-split. It is demonstrated that, employing combinations of a conventional non-polar x polar and a reversed-type polar x non-polar column set, the information content is as high, and the analytical performance is as good as when using two separate GC x GC systems. That is, there is an appreciable gain of time and a reduction of costs without any loss of quality. The general usefulness of performing, and comparing two mutually different GC x GC runs is further illustrated with FAMEs in olive oil, and pollutants in a sediment sample.     

Discovery of powerful uranyl ligands from efficient synthesis and screening

New tripodal gem-(bis-phosphonates) uranophiles were discovered by a screening method that allowed for the selection of ligands with strong uranyl-binding properties in a convenient microtiter-plate format. The method is based on competitive uranium binding by using Sulfochlorophenol S as chromogenic chelate. This dye compound was found to present high uranyl complexation properties and allowed to highlight ligands presenting association constants for UO(2+)(2) up to 10(18) at pH 7.4 and 10(20) at pH 9. A collection of 40 known ligands including polycarboxylate, hydroxamate, catecholate, hydroxypyridonate and hydroxyquinoline derivatives was tested. Also screened was a combinatorial library prepared from seven amine scaffolds and eight acrylates bearing diverse chelating moieties. Among these 96 tested candidates, a tripod derivative bearing gem-bis-phosphonates moieties was found to present the highest complexation properties over a wide range of pH and was further studied.     

Conjugated oligomers with terminal donor-acceptor substitution

Conjugated oligomers represent a prominent class of compounds from a viewpoint of their theory, synthesis, and applications in materials science. Push-pull substitution with an electron donor D at one end of the conjugation and an electron acceptor A at the other end results in them having outstanding optical and electronical properties. This Review highlights fundamental synthetic strategies for the preparation of such oligomers with n repeat units (n=1, 2, 3, 4, ..) and the rules that govern their linear and nonlinear optical properties (absorption, frequency doubling and tripling). The unification of chemical, physical, and theoretical aspects with an interdisciplinary image of this class of compounds is attempted herein.     

Eine Reaktion auf acyclische Carbons?ureanhydride

Ohne Zusammenfassung     

Das Verhalten von Mono- und Diorganylphosphansulfiden gegenüber Metallcarbonylsystemen. VIII [1]; Die Kristall- und Molekülstruktur von Pentacarbonyl(dimethylmercaptophosphan)-chrom

Inhaltsübersicht. Die S-verknüpfte Verbindung (OC)₃CrSPH(CH₃)₂ isomerisiert sich oberhalb 25°C zu dem Mercaptophosphan-Komplex (OC)₅CrP(CH₃)₂SH. Dieser kristallisiert monoklin in der Raumgruppe P2₁/c mit den Citterkonstanten a = 6,882, b = 13,290, c = 13,224 Å, β = 91,60° und vier Molekeln in der Elementarzelle. In der Kristallstruktur (R = 0,085) sind die Chromatome pseudooktaedrisch koordiniert von fünf CO-Gruppen und dem Mercaptophosphanliganden (Cr—P = 2,344 Å). The Behaviour of Mono- and Diorganylphosphane Sulphides towards Metal Carbonyl Systems. VIII. Crystal and Molecular Structure of Pentacarbonyl(dimethylmereaptophosphane) chromium Abstract. The S-linked compound (OC)₅CrSPH(CH₃)₂ isomerizes to the mercaptophosphane complex (OC)₅CrP(CH₃)₂SH above 25°C. The latter crystallizes monoclinic in the space group P2₁/c with the lattice constants a = 6.882, b = 13.290, c = 13.224 Å, β = 91.60° and four molecules per unit cell. In the crystal structure (R = 0.085) the chromium atoms are pseudooctahedrally coordinated by five CO groups and the mercaptophosphane ligand (Cr—P) = 2.344 Å).     

Direct measurement of Fano-effect on Rb at 266 nm

Polarization of photoelectrons from Rb produced by circularly polarized light (λ = 266 nm) was measured to be 68 ± 5%. This value agrees with earlier indirect measurements of the Fano effect on Rb.     

On Direct and Pair Correlation Functions of the Crystalline State and the Crystal-Liquid Phase Boundary

Assuming a non-constant single particle density suitable to describe a bulk crystalline state and a crystal-liquid phase boundary, the coupled ORNSTEIN -ZERNIKE and PERCUS -YEVICK equation to determine the direct and the pair correlation for a one-component LENNARD-JONES system are approximately solved. A hard core reference system is defined within a perturbation treatment; the corrections resulting from the true interaction can be calculated straighforward if the hard core solutions are known. The approximation involves a new class of exact solutions for the limiting case of strongly localized single particle densities.