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  • 1975-1979  (5)
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  • 1
    Electronic Resource
    Electronic Resource
    Copenhagen : International Union of Crystallography (IUCr)
    Acta crystallographica 34 (1978), S. 3616-3623 
    ISSN: 1600-5740
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 320 (1978), S. 539-550 
    ISSN: 0021-8383
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Kinetics of Hydrogen-Deuterium-Exchange in the Methin Chain of Simple PolymethinesSimple polymethines are deuterated in the methin chains at positions of high π-electronic density. The rate constants of this reaction were determined by 1H-n.m.r. spectroscopy taking into account hydrolytic side-reactions. The rate constants of the H/D exchange correlate well with the HMO localization energies at the methin atoms concerned.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 318 (1976), S. 321-326 
    ISSN: 0021-8383
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Solvent-induced Changes of the Electronic Structure of Negatively Solvatochromic DyesThe 1H NMR chemical shifts of negatively solvatochromic dyes depend on the polarity of the solvent used. The differences of the chemical shifts of vicinal protons decrease with increasing polarity. This result supports the idea that the electronic structure of negatively solvatochromic dyes changes from a polymethine-like state in non-polar solvents to a polyene-like state in polar solvents.
    Notes: Die chemischen Verschiebungen des Protonenresonanzspektrums von negativ solvatochromen Farbstoffen hängen von der Polarität des verwendeten Lösungsmittels ab, wobei die Differenzen der chemischen Verschiebungen benachbarter Protonen mit zunehmender Polarität abnehmen. Dies deutet auf eine lösungsmittelinduzierte Veränderung der Elektronenstruktur von einem mehr polymethinähnlichen Zustand in unpolaren Lösungsmitteln in Richtung auf einen polyenähnlichen Zustand in polaren Lösungsmitteln hin.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 318 (1976), S. 993-1007 
    ISSN: 0021-8383
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: CNDO/2 and VESCF-LCAO-MO Calculations of the Simplest Cyanines, Merocyanines, and OxonolesThe wave-functions and eigen-values of the simplest cyanines, merocyanines and oxonoles are calculated by means of the CNDO/2 method. From the charge distribution of the Σ-electrons obtained in this way the parameters of calculations by means of the VESCF-LCAO-MO method are determined. Thus one gets VESCF wave-functions which are free from special parametrisations. The calculated molecular parameters correlate well with experimental data, i.g. dipole moments, transition energies, transition probabilities, and n.m.r. parameters.
    Notes: Die Wellenfunktionen und Eigenwerte der einfachsten Cyanine, Merocyanine und Oxonole werden nach der CNDO/2-Methode berechnet. Aus der erhaltenen Ladungs-verteilung der Σ-Elektronen werden die Parameter für VESCF-LCAO-MO-Berechnungen bestimmt. Auf diese Weise erhält man im Rahmen der π-Elektronennäherung VESCF-Molekülwellenfunktionen, die von speziellen Parametrisierungen frei sind und in befriedigender Weise mit experimentellen Parametern, wie Dipolmomenten, Übergangsenergien, Übergangswahrscheinlichkeiten und NMR-Parametern korrelieren.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 318 (1976), S. 643-657 
    ISSN: 0021-8383
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Molecular Refractivity and Electronic Polarizability of Simple Polymethine DyesThe molecular refractivity and the electronic polarizability of simple cyanines and merocyanines are determined experimentally in different solvents in dependence of the chain length of the polymethines. Comparing molecules of equal size, the cyanines have the highest polarizability of unsaturated organic compounds observed so far. The electronic polarizability of the merocyanines depends strongly on the polarity of the solvent used. In non-polar solvents the polarizability is similar to that of polyenes with comparable size, whereas it reaches nearly the high amount of ideal polymethines in polar solvents.
    Notes: Die Molrefraktion und die elektronische Polarisierbarkeit von einfachen Cyaninen und Merocyaninen werden experimentell in Abhängigkeit von der Polymethinkettenlänge in verschiedenen Lösungsmitteln bestimmt. In Bezug auf gleiche Molekülgröße besitzen die Cyanine die höchste Polarisierbarkeit aller bisher bekannten, ungesättigten organischen Verbindungen. Die elektronische Polarisierbarkeit der Merocyanine ist stark lösungsmittelabhängig. In unpolaren Lösungsmitteln nähert sie sich Werten, die bei Polyenen vergleichbarer Molekülgröße auftreten. In polaren Lösungsmitteln wird die hohe Polarisierbarkeit idealer Polymethine nahezu erreicht.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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