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141.
Chloro-dimethylaminosulfonium Salts. Preparation and I. R. Spectra By reaction of bis-dimethylamino-mono- resp. -disulfane with a mixture of chlorine/antimony(V) chloride the chloro dimethylaminosulfonium hexachloroantimonates(V) [(CH3)2N]2SCI⊕SbCl6? (I) and (CH3)2NSCI2⊕SbCl6? (II) are yielded. The i. r. spectra of these compounds were measured and assigned. 相似文献
142.
Wolfgang Merz 《Fresenius' Journal of Analytical Chemistry》1961,181(1):147-158
Zusammenfassung Es wird über eine modifizierte Methode zur mikroanalytischen Bestimmung des aktiven Wasserstoffs in organischen Substanzen berichtet. Die von Lieb und Schöniger, als Ersatz der Grignard-Reaktion in die Mikroanalyse eingeführte Umsetzung mit dem wesentlich stärker und auch rascher reagierenden Lithiumaluminiumhydrid, konnte sich trotz vieler Vorteile nicht allgemein durchsetzen. Dies lag in erster Linie daran, daß das reine Lithiumalanat nur in sehr wenigen Lösungsmitteln, die zudem wegen ihres hohen Dampfdruckes für eine exakte Mikrobestimmung ungeeignet sind, löslich ist. Ersetzt man jedoch ein oder mehrere Wasserstoffatome des Alanats durch eine Alkyl- bzw. Alkoxygruppe, so führt dies zu einer wesentlichen Löslichkeitserhöhung. Unter den mög- lichen substituierten Alanaten, die wir auf ihre Brauchbarkeit zur Bestimmung aktiver Wasserstoffatome getestet haben, entsprach insbesondere das Natriumaluminiumdiäthyldihydrid weitgehend unseren Anforderungen. Es ist in Kohlenwasserstoffen, wie auch in stark polaren Lösungsmitteln sehr gut löslich. Dadurch ist auch die Möglichkeit für vergleichende Analysen mit Methylmagnesiumjodid gegeben, wodurch in manchen Fällen auf eine bestimmte Stellung oder auch sterische Hinderung der funktionellen Gruppe in der Molekel geschlossen werden kann. Die Anwendungsbreite wie auch die Genauigkeit der Alanatmethode wird an Hand der Analysendaten zahlreicher Testsubstanzen demonstriert. 相似文献
143.
The goal of this work was the development of a novel type of heterogeneous catalyst, consisting of bare metal nanoparticles
on stainless steel foils, which can be shaped to any kind of architecture and, if necessary, heated electrically. Solutions
of pre-prepared, ligand protected and monodispersed gold, palladium, platinum and rhodium nanoparticles were sprayed onto
stainless steel foils, followed by the careful removal of the ligand molecules by an oxygen plasma treatment. Due to this,
bare particles become irreversibly fixed on the steel support. It could be shown that the original particle sizes do not change
during the plasma treatment. Foils, densely coated with the nanoparticles, were used for gas phase catalyses in a self-made
reactor at room temperature or at 60 °C. Hydrogenation of 1,3-butadiene at 15 nm Pd and 2 nm Pt, CO oxidation at 16 nm, 8 nm
and 1.4 nm gold and NO reduction with NH3 at 2 nm Rh particles were performed, indicating that the novel catalysts might in principle be applicable in technical processes
if the experimental conditions like form and temperature would be optimized.
Dedicated to Professor Dieter Fenske on the occassion of his 65th birthday. 相似文献
144.
Solution equilibrium studies on Cu(II)-, Ni(II)- and Zn(II)-N-Me-β-Alaninehydroxamic acid (N-Me-β-Alaha), -N-Me-α-alaninehydroxamic acid (N-Me-α-Alaha), -Imidazole-4-carbohydroxamic acid (Im-4-Cha), -N-Me-imidazole-4-carbohydroxamic acid (N-Me-Im-4-Cha) and -Imidazole-4-acetohydroxamic acid (Im-4-Aha) systems have been performed by pH-potentiometry, UV–Vis spectrophotometry, EPR, CD, ESI-MS and 1H NMR methods. According to the results: (i) the amino-N atoms are more basic in N-Me-α-Alaha and N-Me-β-Alaha than the hydroxamate function, but the trend is just the opposite between the imidazole-N(3) and hydroxamate. (ii) The metal ion anchor is always the hydroxamate part in the amino acid derivatives, while it is always the imidazole-N(3) in the studied imidazolehydroxamic acids. (iii) The three studied N-Me derivatives do not form metallacrowns. Only hydroxamate type chelate is formed with N-Me-β-Alaha, but with N-Me-α-Alaha a new type of coordination mode (via amino-N and hydroxamate-O) also exists. N-Me-Im-4-Cha also forms a dinuclear complex, [M2L3], with Cu(II) and Ni(II) (but not with Zn(II)). In this complex, one of the three ligands might bridge the two metal ions (five-membered hydroxamate-(O,O) plus five-membered (Nim, Ocarb) bridging bis-chelating mode), while each of the additional two ligands binds to one metal. (iv) The two studied N–H derivatives, having dissociable proton on the hydroxamic-N, are able to form metallacrown species. A pentanuclear complex, [M5L4H−4], is exclusively formed above pH 4 between Cu(II) and Im-4-Aha. Interestingly, this 12-metallacrown-4 type complex, although together with various mononuclear binding isomers, appears also with Ni(II) and Zn(II). Unfortunately, the complexes of Im-4-Cha are not soluble in water at physiological pH at all. 相似文献
145.
Wolfgang Marterer Horst Prinzbach Grety Rihs Jakob Wirz Jaques Lecoultre Edgar Heilbronner 《Helvetica chimica acta》1988,71(8):1937-1965
The propensity of the N?N bond to undergo photo [2 + 2] cycloadditions has been further explored. In the specifically designed 1,5-azo/enes 1–3 , no [2 + 2] cycloaddition has been observed upon either direct or sensitized excitation with light of various wave lengths at temperatures down to 77 K, in line with expectations based on X-ray ( 1 : d = 2.71 Å, ω = 129°) and PE measurements ( 1 : I1 = 8.00, I2 = 9.05 eV; 2 ; I1 = 8.00, I2 = 9.25eV). The steric/stereoelectronic demands for the participation of the N?N bond in pericyclic reactions are clearly more stringent than those for the C?C bond. 相似文献
146.
Pd(dba)2[dba = dibenzylideneacetone]/PPh3-or Pd(PPh3)4-catalyzed cyclizations of acetoxy-dienes 2 → 3 and 10 → 11 gave 1-vinyl-2-methylidene-subsituted cyclopentances and cyclohexanes in high yield, consistent with a palladium-ene/β-elimination mechanism ( D → E → F , Scheme 2). The efficient and highly stereoselective cyclizations 7 → 7 and 8 → 9 illustrate intramolecular allylpalladium insertions into 1,2-dialkyl-, trialkyl-, trialkyl-, and cyclic alkenes followed by elimination of the exocyclic β–H giving 1,2-divinylcyclopentanes. These new olefin insertions proceed faster in AcOH (compared to THF) and occur preferentially cis relative to the Pd ( 13 → 14 → 15 ). 相似文献
147.
Wolfgang Oppolzer Mark Kurth Daniel Reichlin Frank Moffatt 《Tetrahedron letters》1981,22(27):2545-2548
The chiral induction in the Diels-Alder addition → , assessed reliably by 19F-NMR-spectroscopy of the endo-esters , varied between 47 - 93% in favor of the 2-(R)-adducts depending on the auxiliary chiral group and the Lewis-acid catalyst. 相似文献
148.
A graphite rod electrothermal atomizer has been used for the AAS determination of traces of gold in hydrochloric and in hydrobromic acid solutions, and also after extraction into HBr-saturated methyl isobutyl ketone. Photographic film samples were decomposed first by enzyme action then by nitric acid/peroxide oxidation, and the gold was extracted into MIBK. For 10-μl aliquots of solution the 3s limits of detection were 3 × 10?10g for aqueous solutions, 7 × 10?10g for MIBK, and 7 × 10?9 g/cm2 for film. 相似文献
149.
Wolfgang Reischl Harald Bernhard Christoph Kratky Erich Zbiral 《Monatshefte für Chemie / Chemical Monthly》1985,116(6-7):831-839
Epoxidation of vitamin D3 with benzonitrile ¦H2O2¦ KHCO3 (Payne's reagent) yields exclusively the 5,6-mono-oxirane2. Further epoxidation with the same reagent gives the 5,6-7,8-bisepoxide3 a. Its stereochemistry and therefore the stereochemistry of2 was established by single crystal X-ray analysis of thep-Brbenzoate3b. Thereby for the first time a directive effect of a homoallylic hydroxyl group during thePayne-epoxidation was established.
Herrn Prof.Mihailovic (Universität Belgrad) mit den besten Wünschen zum 60. Geburtstag gewidmet. 相似文献
150.
The enantiomerically pure (+)-3-methoxy-1, 3, 5 (10)-estratrien-11, 17-dione 11 (with trans-anti-trans configuration) was synthesized in a highly stereocontrolled fashion from (±)-t-butyl 4-methoxy-1-benzocyclobutene carboxylate (8) and the (+)-carboxylic acid 6 , obtained from 4 in two steps, followed by one crystallization of the (+)-ephedrine salt. The key step 10→11 (Scheme 2) involves a thermal intramolecular cycloaddition reaction. 相似文献