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  • 1
    ISSN: 0887-624X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The quenching of pyrene fluorescence by nitromethane, Tl+, Cu2+, I-, and 4-dimethylaminopyridine (DMAP) in aqueous solutions of a pyrene substituted poly(acrylic acid) (1) was influenced by the “polyelectrolyte effect” of 1. The efficiency of quenching in solutions of 1 was measured in terms of the Stern-Volmer constants for dynamic and static quenching which were obtained from comparison of the intensity and lifetime of pyrene fluorescence in solutions of 1 and a monomer model compound. The efficiency of quenching in solutions of 1 was always greater at high pH (9) in comparison to that at low pH (4). The ionization of carboxylic groups in 1 caused an expansion of the polymer mainchain and concomitant exposure of the pyrene molecules to the aqueous phase and quencher. The polyanion domain of 1 favored the condensation of cationic quenchers and could account for very efficient quenching in case of Cu2+ and Tl+. A very efficient quenching of pyrene fluorescence in solutions of 1 by DMAP at high pH was attributed to the hydrophobic interactions of DMAP and pyrene moiety. The iodide ions were less efficient quenchers of pyrene fluorescence due to electrostatic repulsion from the polyanion. The efficiency of quenching by nitromethane was not significantly affected by ionization of the carboxylic groups in 1.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 3 (1970), S. 145-154 
    ISSN: 0030-493X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The low resolution mass spectra of several di-, tri-and tetra-methylated cyclobutanones were determined at high and low ionizing voltages. The spectra are discussed in terms of the competition between loss of CO or loss of a ketene from the molecular ion of the cyclobutanone. The mass spectral results are correlated with the known photochemical behavior of the cyclobutanones and possible mechanistic implications are discussed.
    Additional Material: 4 Tab.
    Type of Medium: Electronic Resource
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