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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Chromatographia 48 (1998), S. 127-132 
    ISSN: 1612-1112
    Keywords: Gas chromatography-mass spectrometry ; Solid-phase microextraction ; Headspace analysis ; Unsaturated aldehydes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A fast and simple headspace SPME sampling method has been developed for quantification of volatile aliphatic aldehydes in sunflower oil. Analysis has been performed by gas chromatography, on a 30m×0.25 mm i.d. ×0.25 μm CP-Wax 52CB column, with mass spectrometric detection. Carryover from the SPME fiber could be eliminated by heating the fiber in the injection port between runs. Response factors of all the compounds were linear for concentrations up to 100 ng μL−1. The slopes of the calibration curves decrease with the amount of saturation of the aldehydes. The average responses for unsaturated aldehydes were twice as high as those for the saturated variety. Responses for dienes were approximately one order of magnitude higher than for saturated aldehydes. Depletion of the analyte was examined by repeated extraction from the same vial. SPME was optimized—after 30 min extraction most components were found to have reached equilibration. The detection limit for the compounds studied varied between 0.1 and 1 ng μL−1. Distribution constants were determined for ten different aldehydes and Henry's constants were calculated for unsaturated aldehydes. There was a definite relationship between the response factors and the amount of saturation of the aldehydes.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 17 (1985), S. 271-275 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Decomposition of 1-phenylethyl-hydroperoxide has been studied in the presence of 2,6-di-tert-butyl-4-methyl-phenol inhibitor in ethylbenzene and chlorobenzene both in oxygen and nitrogen. The oxygen consumption and the inhibitor concentrations were measured against the initial inhibitor concentrations. Two methods were applied for the determination of the rate coefficients of the reaction: \documentclass{article}\pagestyle{empty}\begin{document}$$ {\rm HROOH + InH}\mathop {\hbox to 30pt{\rightarrowfill}}\limits^{k_1 } {\rm HRO}^{\rm .} + {\rm In}^{\rm .} + {\rm H}_{\rm 2} {\rm O} $$\end{document} Its value is about 3 × 10-4L × mol-1 × S-1, at 120°C. However, large experimental errors we deal with, the existence of a reaction yielding radicals, presumably an interaction between hydroperoxide and inhibitor molecules, can be established emphasizing the importance of measurements carried out with various initial concentrations of the inhibitor.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 25 (1993), S. 249-263 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Absolute rate constants for the addition of the 2-cyano-2-propyl radical to 26 alkenes CH2=CXY at 315 K were determined in solution by time-resolved electron-spin-resonance spectroscopy. They vary with the alkene substituents from 30 M-1 s-1 to 7′010 M-1 s-1. For styrene the temperature dependence is given by log k/M-1 s-1 = 7.7 - 26.1/Θ where Θ = 2.303 RT in kJ/mol. An analysis of the substituent effects in terms of polar and enthalpic factors reveals a dominant influence of the overall reaction enthalpy. © 1993 John Wiley & Sons, Inc.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 25 (1993), S. 913-920 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Absolute rate constants for the addition of the 2-hydroxy-2-propyl radical to 18 substituted alkenes (CH2 = CXY) were determined at (296 ± 1) K in 2-propanol by time-resolved electronspin-resonance spectroscopy. With alkene substitution the rate constants vary by more than 6 orders of magnitude. For 3,3-dimethyl-but-1-ene the temperature dependence is given by log k/M-1 · s-1 = 6.4 minus;; 19.1/Θ where Θ = 2.303 RT in kJ/mol-1. As shown by a good correlation with the alkene electron affinities, log k296/M-1 · s-1 = 6.46 + 1.71 · EA/eV (r = 0.930), 2-hydroxy-2-propyl is a very nucleophilic radical, and its addition rates are highly governed by polar effects. © 1993 John Wiley & Sons, Inc.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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