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141.
The absorptiostat method previously described is used for the catalytic-kinetic determination of sulphur compounds (sulphide, thioacetamide. thiourea and thiosulphate) in the micromolar range by means of their catalytic action for the indigo carmine—hydrogen peroxide indicator reaction. The thiosulphate catalyst is activated by iron(III) or aluminium(III); aluminium(III) is deactivated by fluoride. On this basis, iron(III) is determined in the ng range, and aluminium(III) and fluoride in the μg range. 相似文献
142.
Herbert Schumann Kerstin Zietzke Frank Erbstein Roman Weimann 《Journal of organometallic chemistry》1996,520(1-2):265-268
LnCl3 reacts with Na(C5Me41Bu) in THF to form the organolanthanoid chlorides [(C5Me41Bu)2LnCl(THF)] (Ln = La (1a), Lu (1b)). Compounds 1a and 1b yield in reaction with NaO2CCH3 the monomeric organolanthanoid acetates [(C5Me41Bu)2LnO2CCH3] (Ln = La (2a), Lu (2b)). The single crystal X-ray structure analysis of 2b as well as the cryoscopic molecular weight investigation of 2a verify the monomeric structure of these complexes. 相似文献
143.
Braulio Insuasty M
Nica Ramos Jairo Quiroga Adolfo Sanchez Manuel Nogueras Norbert Hanold Herbert Meier 《Journal of heterocyclic chemistry》1994,31(1):61-64
The reaction of 4,5-diamino-1,6-dihydropyrimidin-6-ones 1 with one equivalent of the chalcones 2 leads in an acidic medium to the formation of the 2,4-diaryl-2,3,6,7-tetrahydro-1H-pyrimido[4,5-b][1,4]diazepin-6-ones 3a-m . The structure elucidation of the products is based on detailed nmr investigations including selective 13C[1H] decoupling experiments. 相似文献
144.
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146.
Titanium (IV) chloride and silicon (IV) chloride with high oxygen affinity are the best Lewis acid catalysts, of a number tested, for cyclisation of an enamine-ketone (1) leading to the alkaloid, julandine (2); cyclisation of (6) in methanol solution without catalyst yields -methylipalbidine (7) . 相似文献
147.
Capillary electrochromatography (CEC) was employed as a rapid and high-efficiency method for the isocratic separation of all 20 important phenylthiohydantoin (PTH) amino acids, the end products of Edman degradation during N-terminal protein sequencing. For this purpose, 75 microm ID fused-silica capillaries were packed with standard 3 microm Hypersil octadecyl silica (ODS) particles using a two-step column fabrication process, which represents a fast, reliable and efficient means of producing long-term stable columns. The influence of solvent composition, pH, type of buffer cation, buffer concentration, and temperature on retention behavior of PTH amino acids was investigated. Same-day and day-to-day reproducibility of the retention times (over a period of two months) were found to be better than 3%. When comparing this new technique with traditional reversed phase-high performance liquid chromatography (RP-HPLC) methods applied in automated protein sequenators, CEC shows essentially shorter separation times and superior resolution. 相似文献
148.
Weisz A Andrzejewski D Fales HM Mandelbaum A 《Journal of mass spectrometry : JMS》2001,36(9):1024-1030
Positionally isomeric 2-(2-quinolinyl)-1H-indene-1,3(2H)-dione mono- and disulfonic acids give rise to similar electrospray ionization (ESI) and atmosphere pressure chemical ionization (APCI) mass spectra, which show very abundant MH(+) ions and negligible fragmentation. The MH(+) ions of these isomeric acids exhibit notably different behavior under collision-induced dissociation (CID) conditions. The acids with a sulfonic group at position 8' in the quinoline moiety, adjacent to the N-atom, exhibit highly abundant [MH - H(2)SO(3)](+) ions (m/z 272 for the mono- and m/z 352 for the disulfonic acids), which are of lower abundance in the CID spectra of isomers with the SO(3)H group at other positions, remote from the nitrogen atom. The latter isomers undergo efficient eliminations of SO(3) and HSO(3). The isomeric diacids with one SO(3)H group at position 4 of the indene-1,3(2H)-dione moiety, adjacent to one of the carbonyl groups, undergo highly efficient elimination of H(2)O. Mechanistic pathways, involving interactions between adjacent groups, are proposed for the above regiospecific fragmentations. Pronounced different behavior has been also observed in negative ion tandem mass spectrometric measurements of the sulfonic acids. The distinctive behavior of the isomeric acids was strongly pronounced when the measurements were performed with an ion trap mass spectrometer (LCQ), and much less so with a triple-stage quadrupole instrument (TSQ). 相似文献
149.
J. Herbert Hall Joseph Yuming Chien Joel M. Kauffman Peter T. Litak Jeffrey K. Adams Ronald A. Henry Richard A. Hollins 《Journal of heterocyclic chemistry》1992,29(5):1245-1273
A number of 5-aryl-2-(4-pyridyl)oxazoles, a 2-aryl-5-(4-pyridyl)oxazole, the related oxadiazole and furan, several 2-(4-pyridyl)cycloalkano[d]oxazoles, and many of their quaternary salts were prepared. No single standard synthesis was effective for preparation of more than a few of the 25 free bases described; methods often unique to a base were employed. Minor variations in structure sometimes produced large differences in absorption and emission wavelengths, as well as in the magnitude of the extinction coefficient. The salts are of interest as laser dyes, scintillation fluors, biological stains, and shifters for luminescent solar concentrators. 相似文献
150.
Herbert Weisz 《Mikrochimica acta》1954,42(3-4):376-387
Zusammenfassung Mit Hilfe der bereits früher beschriebenen Ringofenmethodik wurde ein Trennungsgang ausgearbeitet, der folgende Ionen berücksichtigt: Pb, Bi, Cu, Cd, Sn, Sb, Fe, Co, Ni, Mn, Cr, Zn, Al, Ti. Zur Analyse reicht ein Tropfen von etwa 1,5l aus, soferne die darin enthaltenen Mengen die Durchführung einer Identitätsreaktion noch gestatten. Die Ionen werden in vier Gruppen getrennt, die als Ring I, II und III und Tüpfelfleck bezeichnet werden. Die Nachweisreaktionen werden auf dem Papier mit Hilfe bereits bekannter, für diesen speziellen Zweck aber abgewandelter Reaktionen durchgeführt. Vier Beispiele werden angeführt, bei denen mit 35g und weniger gearbeitet wurde. Die Analyse nimmt nur etwa eine Stunde in Anspruch.
Für das gro\e Interesse und die stete Förderung meiner Arbeit erlaube ich mir an dieser Stelle dem Vorstand des Institutes, Herrn o. ö. Prof. Dr.Robert Strebinger, meinen ergebensten Dank auszusprechen. 相似文献
Summary With the aid of the ring furnace method previously described, it has been possible to work out a method of separation taking account of following ions: Pb, Bi, Cu, Cd, Sn, Sb, Fe, Co, Ni, Mn, Cr, Zn, Al, Ti. A drop of about 1.5l is sufficient for the analysis, provided the amounts of the cations present still permit the identification reactions. The ions are separated into 4 groups, designated as Ring I, II, III, and fleck. The detection reactions are conducted on the paper with the aid of familiar reactions, which however have been modified for this particular purpose. Four examples are cited, employing 35g or less. The analysis requires only about one hour.
Résumé Au moyen de la méthode du four annulaire déjà décrite, on a élaboré une méthode de séparation qui concerne les ions suivants: Pb, Bi, Cu, Cd, Sn, Sb, Fe, Co, Ni, Mn, Cr, Zn, Al, Ti. Pour l'analyse une goutte de 1,5 l suffit en tant que les quantités contenues permettent encore l'exécution d'une réaction d'identification. Les ions sont séparés en quatre groupes qui sont désignés par anneau 1, 2, 3 et tache de goutte. Les réactions d'identification sont exécutées sur papier au moyen d'essais déjà connus mais modifiés pour ce but spécial. On donne le mode opératoire pour quatre exemples exécutés avec 35g et mÊme moins. L'analyse ne demande qu'une heure.
Für das gro\e Interesse und die stete Förderung meiner Arbeit erlaube ich mir an dieser Stelle dem Vorstand des Institutes, Herrn o. ö. Prof. Dr.Robert Strebinger, meinen ergebensten Dank auszusprechen. 相似文献