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  • 1
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 122 (1989), S. 315-320 
    ISSN: 0009-2940
    Keywords: Acetylacetone, hexafluoro- ; Diol formation / Enolization ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Eine spektroskopische und mechanistische Untersuchung der Enolisierung und Diol-Bildung von Hexafluoracetylaceton in Gegenwart von Wasser und AlkoholDie Reaktionen von Hexafluoracetylaceton (Hfac) (6) mit Wasser, Methanol, Ethanol und Isopropylalkohol wurde im einzelnen anhand von 1H-, 13C-, 17O-, 19F-NMR- und UV-VIS-Spektroskopie untersucht. Dabei konnten die Zwischen- und Reaktionsprodukte bei der Enolisierung und Diol-Bildung spektroskopisch identifiziert werden. Die vorgeschlagenen Reaktionswege werden unter Bezug auf früher in der Literatur berichtete Daten diskutiert. Ein wichtiges Ergebnis dieser Untersuchung ist der direkte Nachweis für die Bildung der Addukt-Spezies Hfac(OH)4 (10), Hfac(OMe)2 (13a) und Hfac(OEt)2 (13b).
    Notes: The reactions of hexafluoroacetylacetone (hfac) (6) with water, methanol, ethanol, and isopropyl alcohol were studied in detail using 1H-, 13C-, 17O-, 19F-NMR, und UV-VIS spectroscopy. The reported spectra enable the identification of intermediate and product species, and allow a mechanistic analysis of the enolization and diol formation. The suggested mechanisms are discussed with reference to earlier data reported in the literature. An important feature of this study is the direct evidence presented for the formation of the adduct species hfac(OH)4 (10), hfac(OMe)2 (13a), and hfac(OEt)2 (13b).
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1434-1948
    Keywords: Cytochrome c ; Chromium(v) ; Saturation kinetics ; Separation of K and kET ; Volume profile ; Kinetics ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The irreversible outer-sphere electron-transfer reaction between trans-bis(2-ethyl-2-hydroxybutanoato(2-))oxochromate(v) and cytochrome cII was investigated as a function of pH, concentration, temperature and pressure. The plot of the observed pseudo-first order rate constant as a function of the CrV concentration shows a clear trend towards saturation at higher CrV concentrations, from which the precursor formation constant and the electron-transfer rate constant could be separated (K = 37 ± 5 M-1 and kET = 1510 ± 180 s-1 at pH 4.8 and 279 K). In the low CrV concentration range the second-order electron-transfer rate contants were measured as a function of temperature (ΔH# = 20.9 ± 0.6 kJ mol-1; ΔS# = -79.9 ± 2.1 J K-1 mol-1; ΔG# (279 K) = 43.2 kJ mol-1). High-pressure experiments were performed at two different pH values. The kinetic (stopped-flow) and thermodynamic (electrochemical) measurements as a function of pressure enabled the construction of a volume profile for the system at 279 K. The activation volumes for the redox process are -9.2 ± 0.2 (pH 5.0) and -11.1 ± 0.8 cm3 mol-1 (pH 4.7), and the overall reaction volumes were estimated to be -7 ± 2 (pH 5.0) and -10 ± 2 cm3 mol-1 (pH 4.7) . The transition state of the redox reaction lies to a large extent on the product side and can be described as “late”. The results are discussed in comparison to earlier measurements using cobalt and ruthenium complexes as reaction partners for cytochrome c.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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