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  • Wiley-Blackwell  (208)
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  • 1
    ISSN: 0935-9648
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 0941-1216
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Regio- and Stereospecific Addition of Diazomethane to Gibberellic Acid: A New Effective Pathway to 1α,2α-MethylenegibberellinsA new pathway to 1α,2α-methylenegibberellines via pyrazoline intermediates is reported. In contrast to the addition of diazomethane to the Δ1-double bond of corresponding enones in the case of 1 “Umpolung” of the regioselectivity with cis-addition from the α-side to give pyrazoline ester 4 is observed. Subsequent photolysis of 4 leads to the 1,2-cyclopropyl derivative 6. The structures of the key compounds 4 and 6 are confirmed especially by n.m.r. and X-Ray analysis.
    Additional Material: 2 Ill.
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  • 3
    ISSN: 0021-8383
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Mass Spectrometry of Natural Products. XV. Comparative Positive-Negative Ion Mass Spectrometry of AzidogibberellinsThe fragmentation behaviour of 1-azido-3-hydroxy-gibberellin derivatives has been studied by means of positive and negative ion mass spectrometry, high resolution and metastable transitions. The results obtained allow a mass spectrometric distinction to be made between epimers with different stereochemistry of the ring A substituents.
    Additional Material: 6 Ill.
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  • 4
    Publication Date: 2024-03-21
    Description: The continental expression of global cooling during the Miocene Climate Transition in Central Asia is poorly documented, as the tectonically active setting complicates the correlation of Neogene regional and global climatic developments. This study presents new geochemical data (CaSO 4 content, carbonate δ 13 C and δ 18 O) from the endorheic alluvial‐lacustrine Aktau succession (Ili Basin, south‐east Kazakhstan) combined with findings from the previously published facies evolution. Time series analysis revealed long‐eccentricity forcing of the paleohydrology throughout the entire succession, split into several facies‐dependent segments. Orbital tuning, constrained by new laser ablation U‐Pb dates and a preexisting magnetostratigraphy, places the succession in a 5.0 Ma long interval in the middle to late Miocene (15.6 to 10.6 Ma). The long‐term water accumulation in the Ili Basin followed the timing of the Miocene Climate Transition, suggesting increased precipitation in the catchment area in response to climate cooling and stronger westerly winds. This was paced by minima of the 2.4 Ma eccentricity cycle, which favored the establishment of a discharge playa (~14.3 Ma) and a perennial lake (12.6 to 11.8 Ma). Furthermore, low obliquity amplitudes (nodes) caused a transient weakening of the westerlies at ~13.7 to 13.5 Ma and at ~12.7 Ma, resulting in negative hydrological budgets and salinization. Flooding of the windward Ili Basin coeval with aridification in the leeward basins suggests that the Tian Shan was a climate boundary already in the middle Miocene. Our results emphasize the impact of climate fluctuations on the westerlies' strength and thus on Central Asian hydrology.
    Type: Article , PeerReviewed
    Format: text
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  • 5
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 206 (1993), S. 21-38 
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: To improve materials performance like the temperature of deformation under flexural load of thermoplastic polyurethanes (TPU) blending with thermoplastics is sensible. A good compatibilization and phase adhesion of thermodynamical incompatible blend-components can be achieved by the use of the right coupling agents. In the case of blends with TPU and PA6 diisocyanate is given into the melt during the extrusion. Through the chemical reactions effects of compatibilization are achieved in the cases of blends with polyesterpolyurethanes and PA6 produced by extrusion and injection moulding and by reactions in solution, too. These could be perceived as consequence of MDI-initiated reactions within the phase boundary layer. The possible reactions with the PA6-phase will be discussed by the use of a model-system made in solution. No effects of compatibilization by MDI could be proved in the polyetherpolyurethan/PA6-system. The chemical characterization of the blends was realized by GPC and FTIR whereas the properties of the morphology are proved with the help of DSC, DMA and transmission electron microscopy (TEM).
    Notes: Zur Verbesserung der Werkstoffeigenschaften von thermoplastischen Polyurethanen (TPU), wie etwa der Wärmeformbeständigkeit, ist es sinnvoll, ein Blending mit Thermoplasten vorzunehmen. Eine gute Phasenverträglichkeit und Phasenhaftung bei thermodynamisch unverträglichen Blendkomponenten kann durch geeignete reaktive Koppler erreicht werden. Bei den Blends aus TPU and PA6 wird Diisocyanat während der Extrusion in der Schmelze eingebracht. Durch die ablaufenden chemischen Reaktionen werden bei extrudierten und verspritzten Blends und bei aus der Lösung erzeugten Systemen aus Polyesterpolyurethan und PA6 verträglichkeitsverbessernde Wirkungen erreicht. Diese wurden als Folge von mit 4,4′-Diphenylmethandiisocyanat (MDI) initiierten Reaktionen in der Grenzschicht erkannt, wobei die möglichen Reaktionen mit der PA6-Phase anhand eines Modellsystems aus der Lösung diskutiert werden. Bei Blends aus Polyetherpolyurethan und PA6 wurde keine Verträglichkeitsvermittlung durch MDI nachgewiesen. Die chemische Charakterisierung der Blends erfolgte durch GPC und FTIR, während die morphologischen Eigenschaften mittels DSC, DMA und Elektronenmikroskopie dokumentiert wurden.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 100 (1967), S. 2367-2372 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Durch vergleichende kinetische Untersuchungen der Aminolyseaktivität verschiedener Acyl-aminosäure-chinolyl-ester wird der Beweis für einen Reaktionsmechanismus erbracht, durch den die ungewöhnlich hohe Geschwindigkeit und zugleich der racemisierungsfreie Verlauf der Chinolyl-(8)-ester-Aminolyse erklärt werden Kann.
    Additional Material: 2 Ill.
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  • 7
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 99 (1966), S. 2419-2429 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Synthese und Eigenschaften N-geschützter Aminosäure- und Peptid-chinolyl-(8)-ester werden beschrieben. Die durch kinetische Messungen ermittelte hohe Aminolyseaktivität dieser neuen aktivierten Ester findet bei der Peptidsynthese unter präparativen Bedingungen ihre Bestätigung. Zur Darstellung von Dipeptidderivaten in Ausbeuten über 90% genügen Reaktionszeiten von 4 bis 5 Stdn. bei Raumtemperatur. Ein Heptapeptidderivat wird zu 75% aus einem N-geschützten Dipeptid-chinolyl-(8)-ester und einem Pentapeptidester erhalten. Die bei der Aminolyse eliminierte Aktivierungskomponente läßt sich mit 2n Säuren quantitativ entfernen.  -  Bei Peptidsynthesen mit der Chinolyl-(8)-ester-Methode tritt keine Racemisierung auf.
    Additional Material: 4 Tab.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 99 (1966), S. 2944-2954 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Von den möglichen Halogenderivaten des 8-Hydroxy-chinolins eignen sich besonders das 5-Chlor- und 5.7-Dichlor-8-hydroxy-chinolin zur Carboxylaktivierung. Die neuen aktivierten Ester kristallisieren ausgezeichnet und sind sehr beständig. Mit Hilfe kinetischer Messungen wird der Einfluß der Halogensubstitution auf die Aminolyseaktivität bestimmt. Unter milden Reaktionsbedingungen kuppeln die Benzyloxycarbonyl-aminosäure-[5-chlor-chinolyl-(8)-ester] mit Aminosäureestern und Natriumsalzen von Aminosäuren in sehr guten Ausbeuten ohne. Racemisierung zu den entsprechenden Peptiden, wobei die eliminierte Aktivierungskomponente mit 2n Säuren quantitativ abgetrennt werden kann. Aus aktivierten Acyldipeptidestern werden eine Reihe von Tri-, Tetra- und Pentapeptid-Derivaten dargestellt.
    Additional Material: 2 Ill.
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  • 9
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 23 (1983), S. 595-611 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The computational considerations involved in calculating ordinary and rotatory intensities and electronic excitation energies in the random phase approximation (RPA) are examined. We employ a localized orbital formulation in order to analyze the results in terms of local and charge-transfer excitations. Occupied orbitals are localized by the Foster-Boys procedure. The virtual space is transformed into a localized “valence” set that maximizes dipole strengths with the occupied counterparts, and a delocalized remainder. The two-electron integral transformation is performed with an efficient algorithm, based on Diercksen's, that generates only the particle-hole-type integrals required in the RPA. The lowest solutions of the RPA equations are obtained iteratively using a modification of the Davidson-Liu simultaneous vector expansion method. This allows the inclusion of the entire set of particle-hole states supported by a basis set of up to 102 orbitals. Calculations at this level give better excitation energies and intensities than SDCI methods, at substantial savings in computational effort. Comparative timings, computed results and analysis in terms of localized orbitals are given for planar and distorted ethylene using extended atomic orbital bases including diffuse functions. The results for planar ethylene are in excellent agreement with experiment.
    Additional Material: 7 Tab.
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  • 10
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 23 (1983), S. 1693-1693 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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