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31.
32.
Franz Heresch Guenter Allmaier Gottfried Heinisch 《Journal of heterocyclic chemistry》1981,18(2):255-258
The electron impact mass spectrometric fragmentation of trans-3- and trans-4-styrylpyridazine is reported in detail, including a comparison with other aza-stilbenes. With regard to a distinction between the two isomeric styrylpyridazines, the intensity ratio of the M+ and [M-1]+ ions, the general degree of fragmentation and the elimination pathways of nitrogen proved to be most characteristic. 相似文献
33.
Max Schmidt und Dieter Franz 《Fresenius' Journal of Analytical Chemistry》1965,215(5):395-400
Zusammenfassung Es wird ein Verfahren zur Bestimmung von Stibin beschrieben, das sich sowohl zur Analyse von SbH3 in organischen Lösungsmitteln als auch zur Bestimmung von flüssigem oder festem SbH3 eignet. Hierbei wird das Stibin mit überschüssigem Brom zu SbV oxydiert, danach mit SO2 zu SbIII reduziert und dieses oxydimetrisch mit Jod oder Bromat titriert.
Herrn Professor Dr. C. Mahr zum 65. Geburtstag gewidmet. 相似文献
Summary A method is proposed for the determination of stibine, applicable to its solutions in organic solvents and also to the solvent-free liquid or solid substance. The procedure involves oxidation of SbH3 with an excess of bromine to SbV, reduction to SbIII with SO2, and oxidimetric titration of the trivalent antimony with iodine or bromate.
Herrn Professor Dr. C. Mahr zum 65. Geburtstag gewidmet. 相似文献
34.
Anthony Herlt Lewis Mander Rymond Rumampuk Wolfgang Steglich Franz von Nussbaum 《Tetrahedron》2004,60(29):6101-6104
Bisdemethylaaptamine (6), a proposed biosynthetic precursor of the aaptamines has been isolated from an Aaptos sp. marine sponge harvested off the Indonesian coast, and its identity confirmed by comparison of its spectral data with that of synthetic material. Bisdemethylaaptamine-9-O-sulfate (7) was also isolated from the same source. This is the first report of a sulfated aaptamine. 相似文献
35.
The development and in-house testing of a method for the detection and quantification of cocoa butter equivalents in cocoa butter and plain chocolate is described. A database consisting of the triacylglycerol profile of 74 genuine cocoa butter and 75 cocoa butter equivalent samples obtained by high-resolution capillary gas liquid chromatography was created, using a certified cocoa butter reference material (IRMM-801) for calibration purposes. Based on these data, a large number of cocoa butter/cocoa butter equivalent mixtures were arithmetically simulated. By subjecting the data set to various statistical tools, reliable models for both detection (univariate regression model) and quantification (multivariate model) were elaborated. Validation data sets consisting of a large number of samples (n = 4050 for detection, n = 1050 for quantification) were used to test the models. Excluding pure illipé fat samples from the data set, the detection limit was determined between 1 and 3% foreign fat in cocoa butter. Recalculated for a chocolate with a fat content of 30%, these figures are equal to 0.3-0.9% cocoa butter equivalent. For quantification, the average error for prediction was estimated to be 1.1% cocoa butter equivalent in cocoa butter, without prior knowledge of the materials used in the blend corresponding to 0.3% in chocolate (fat content 30%). The advantage of the approach is that by using IRMM-801 for calibration, the established mathematical decision rules can be transferred to every testing laboratory. 相似文献
36.
Franzén J Marigo M Fielenbach D Wabnitz TC Kjaersgaard A Jørgensen KA 《Journal of the American Chemical Society》2005,127(51):18296-18304
The development of a general organocatalyst for the alpha-functionalization of aldehydes, via an enamine intermediate, is presented. Based on optically active alpha,alpha-diarylprolinol silyl ethers, the scope and applications of this catalyst for the stereogenic formation of C-C, C-N, C-F, C-Br, and C-S bonds are outlined. The reactions all proceed in good to high yields and with excellent enantioselectivities. Furthermore, we will present mechanistic insight into the reaction course applying nonlinear effect studies, kinetic resolution, and computational investigations leading to an understanding of the properties of the alpha,alpha-diarylprolinol silyl ether catalysts. 相似文献
37.
Zusammenfassung Darstellung und Eigenschaften von Ammonium-, Kalium-, Silber- und Thalliumsalzen des Triselenimides und der Diimidotriselensäure werden beschrieben, Infrarot-Spektren sowieDebye-Scherrer-Diagramme einiger dieser erstmalig dargestellten Verbindungen werden zu ihrer Charakterisierung mitgeteilt.Mit 3 Abbildungen1. Mitt.:A. Engelbrecht undF. Clementi, Mh. Chem.92, 555 (1961). 相似文献
38.
Redl FX Black CT Papaefthymiou GC Sandstrom RL Yin M Zeng H Murray CB O'Brien SP 《Journal of the American Chemical Society》2004,126(44):14583-14599
We have investigated the structural, magnetic, and electronic properties of nonstoichiometric iron oxide nanocrystals prepared by decomposition of iron(II) and iron(0) precursors in the presence of organic solvents and capping groups. The highly uniform, crystalline, and monodisperse nanocrystals that were produced enabled a full structural and compositional survey by electron microscopy and X-ray diffraction. The complex and metastable behavior of nonstoichiometric iron oxide (wüstite) at the nanoscale was studied by a combination of Mossbauer spectroscopy and magnetic characterization. Deposition from hydrocarbon solvents with subsequent self-assembly of iron oxide nanocrystals into superlattices allowed the preparation of continuous thin films suitable for electronic transport measurements. 相似文献
39.
Glyoxaldiimines (I) RN=CHCH=NR show in the NMR a downfield shift of glyoxalic protons (Hgly) when complexed to (II: M = Mo, W), but increasing high field shifts when going to (III) and complexes (IV). In the tungsten complexes II HglyW coupling satellites are resolved (J(WH) ≈4–6 Hz); in the phosphine compounds III, IV long range PHgly coupling is clearly visible. Mechanisms of spinspin interaction are briefly discussed in connection with the EPR results on monoanionic radicals of II–IV. 相似文献
40.
Beker H Boggild H Boissevain J Cherney M Dodd J Esumi S Fabjan CW Fields DE Franz A Hansen KH Holzer EB Humanic TJ Jacak BV Jayanti R Kalechofsky H Kobayashi T Kvatadze R Lee YY Leltchouk M Lörstad B Maeda N Medvedev A Miake Y Miyabayashi A Murray M Nagamiya S Nishimura S Noteboom E Pandey SU Piuz F Polychronakos V Potekhin M Poulard G Sakaguchi A Sarabura M Shigaki K Simon-Gillo J Sondheim W Sugitate T Sullivan JP Sumi Y van Hecke H Willis WJ Wolf K Xu N 《Physical review letters》1995,74(17):3340-3343