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  • Physics  (14)
  • Physical Chemistry  (12)
  • Biochemistry and Biotechnology  (1)
  • 1
    Electronic Resource
    Electronic Resource
    Effect of aliphatic aldehydes on the lipid peroxidation and chemiluminescence of biological systems under oxidative stress (1997)
    New York : Wiley-Blackwell
    Journal of Bioluminescence and Chemiluminescence 12 (1997), S. 141-148 
    Details
    ISSN: 0884-3996
    Keywords: lipid peroxidation ; aldehydes ; chemiluminescence ; oxidative stress ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: The effect of several aliphatic aldehydes on lipid peroxidation was evaluated by measuring the oxygen uptake rate, thiobarbituric acid-reactive products formation and the emitted visible chemiluminescence intensity. Measurements were carried out in brain homogenates and erythrocyte plasma membrane and liver microsomal fractions. In all systems studied, aldehydes (25 mmol/L) (e.g. acetaldehyde, 2,2-dimethylpropanal), increased the intensity of the luminescence associated with the oxidation process. In contrast, aldehyde incorporation decreased TBARS production and the rate of oxygen uptake. The increased luminescence intensity is explained in terms of secondary reactions of aldehyde derived free radicals. These results clearly indicate that extreme care must be exercized in the intepretation of chemiluminescence data in the presence of aldehydes. © 1997 John Wiley & Sons, Ltd.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Photopolymerization of methyl methacrylate sensitized by aliphatic ketones (1979)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Chemistry Edition 17 (1979), S. 19-26 
    Details
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The polymerization of methyl methacrylate photosensitized by several alkyl ketones has been investigated. It was found that alkyl ketones can induce the free radical polymerization of the monomer with an efficiency that increases when the triplet lifetime decreases. For ketones of similar triplet lifetime those decomposing predominantly by a type I photocleavage show greater initiation efficiencies than those that react by a type II mechanism. The results obtained show that quenching of the excited ketones by the monomer does not induce polymerization. For ketones bearing γ-hydrogens the initiation is due to the 1,4-biradical produced by intramolecular hydrogen abstraction.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1979.170170103
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  • 3
    Electronic Resource
    Electronic Resource
    Polymerization photosensitized by carbonyl compounds (1979)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Chemistry Edition 17 (1979), S. 2791-2803 
    Details
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The polymerization of methyl methacrylate and styrene photosensitized by acetone, aldehydes, ethyl pyruvate, 2,3-butanedione, and 2,3-pentanedione has been investigated and the effect of several additives (carbon tetrachloride, cumene, diethyl amine, triethyl amine, 2-pentanol, and tetrahydrofuran) on initiation efficiency has been evaluated. The initiation efficiency of a given system depends on several factors, the most important of which are the relative rates of quenching by the monomers and the additives and type of product obtained.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1979.170170916
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  • 4
    Electronic Resource
    Electronic Resource
    Polymerization photoinitiated by carbonyl compounds. IV. α-diketones and α-substituted alkanones (1982)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Chemistry Edition 20 (1982), S. 73-78 
    Details
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The photoinitiation efficiency of the free-radical polymerization of methyl methacrylate and styrene by several carbonly compounds has been determined. The compounds considered were α-substituted ketones and α-dicarbonyl compounds. For the ketones, the initiation efficiency employing methyl methacrylate depends on the α substitution; the values obtained change from less than 10-3 (acetone) to 0.65 (3-hydroxy-3-methyl-2-butanone). All ketones are more efficient towards methyl methacrylate than styrene. This result can be explained in terms of triplet quenching by the last monomer. The results obtained employing α-dicarbonyl compounds do not conform to a simple pattern. In particular, benzil shows a considerably larger efficiency towards styrene than for methyl methacrylate. Since benzil is efficiently quenched by styrene, the initiation must involve the interaction of an excited benzil molecule and the monomer.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1982.170200108
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  • 5
    Electronic Resource
    Electronic Resource
    2,4-Dimethyl-3-pentanone-sensitized photopolymerization of vinyl monomers (1979)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Chemistry Edition 17 (1979), S. 1645-1653 
    Details
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The initiation quantum yield in the bulk photopolymerization of vinyl monomers sensitized by 2,4-dimethyl-3-pentanone has been measured for several monomers. The results obtained were interpreted in terms of a mechanism that considers singlet and triplet photocleavage of the ketone, competing with the quenching by the monomer. The quenching process does not lead to free radicals that can initiate the polymerization.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1979.170170608
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  • 6
    Electronic Resource
    Electronic Resource
    Photoinitiated polymerization: Effect of the initiator absorbance (1983)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Chemistry Edition 21 (1983), S. 2197-2202 
    Details
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The dependence of the polymerization rate and average chain length on the absorbance of the initiator in the photoinitiated polymerization of vinyl monomers has been evaluated. It is found that a simple model taking into account the spatially inhomogeneous free-radical distribution predicts an order in initiator that changes from 0.5 at low concentration to -0.5 at high concentration. The maximum rate is obtained, irrespective to any other condition, when the absorbance of the initiator is 2.51.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1983.170210804
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  • 7
    Electronic Resource
    Electronic Resource
    Addition of methoxy radicals to olefins (1975)
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 7 (1975), S. 625-631 
    Details
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The addition of methoxy radicals to several olefins has been studied by a competitive method at 127°C in gas phase. The thermal decomposition of dimethyl peroxide was used as methoxy radical source. The rate of addition to the double bond was measured relative to the oxidation of carbon monoxide. For the addition to ethylene it was obtained that \documentclass{article}\pagestyle{empty}\begin{document}$$ k_{{\rm add}} = \left({3.7 \pm 0.8} \right) \times 10^4 M^{ - 1} \cdot {\rm s}^{{\rm - 1}} $$\end{document} This rate constant is similar to the one shown by methyl radicals under similar conditions. From the relative rate of addition to several chlorinated and fluorinated olefins it can be concluded that methoxy radicals show very little “electrophilic” character.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/kin.550070411
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  • 8
    Electronic Resource
    Electronic Resource
    Cage reactions in the photolysis of 2,2,4,4-tetramethyl-3-pentanone (1984)
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 16 (1984), S. 503-511 
    Details
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The product quantum yields in the photolysis of 2,2,4,4-tetramethyl-3-pentanone have been measured in homogeneous solvents of different viscosities, in micellar solutions of cetyltrimethylammonium chloride and sodium dodecyl sulfate, and in dioctadecyl ammonium chloride vesicles.The product quantum yield in n-heptane was found to be 1. This value decreases to 0.5 in paraffin oil as a consequence of geminate recombination. In the presence of free radical scavengers, the extent of geminate disproportionation can be evaluated from the yields of isobutene and 2,2-dimethyl propionaldehyde. From these yields and the geminate recombination yields the total amount of geminate processes and the disproportionation-to-combination ratio for caged radicals are estimated. It is found that micelles provide the most efficient cages. In these media only about 10% of the radicals avoid cage processes. The disproportionation-to-combination ratio of tert-butyl and pivaloyl radicals was found to be extremely media dependent. The measured values ranged from about 0.2 in paraffin oil to 0.8 in cetyltrimethylammonium chloride micelles.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/kin.550160502
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  • 9
    Electronic Resource
    Electronic Resource
    Reactivity of tert-butoxy radicals towards thiols, alkyl sulfides, and alkyl disulfides (1989)
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 21 (1989), S. 245-250 
    Details
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Rate constants for the reactions of tert-butoxy radicals (generated by the thermal decomposition of di-tert-butylperoxyoxalate) with several sulfur containing compounds have been measured at 310 K in benzene. Hexanethiol (k = 6.5 × 107M-1s-1) reacts considerably faster than alkyl sulfides and disulfides. For these compounds the reaction rate constants are slightly dependent on the α-hydrogen type, changing (when it is expressed per hydrogen atom) only a factor 5 for sulfides and 3 for disulfides when the α-hydrogen is changed from primary (methyl) to tertiary (isopropyl). The data obtained are compared to those found for the deactivation of the benzophenone triplet. Values of ktert-butoxy/kbenzophenone range from ca 10-3 (di-tert-butyl disulfide) to 7.5 (hexanethiol). The results obtained are rationalized in terms of bond strength, steric hindrance, and charge transfer contributions to the critical configuration energies.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/kin.550210404
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  • 10
    Electronic Resource
    Electronic Resource
    Kinetics of the reaction between 2,2′-azinobis (3-ethylbenzothiazoline-6-sulfonic acid (ABTS) derived radical cations and phenols (1997)
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 29 (1997), S. 219-224 
    Details
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The reaction between the radical cation derived from 2,2′-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) and phenols follows a kinetic law given by \documentclass{article}\pagestyle{empty}\begin{document}$$ d[ABTS^{\buildrel{+}\over{\cdot}}]/dt=k [ABTS^{\buildrel{+}\over{\cdot}}]^2[PhOH]/[ABTS] $$\end{document} with stoichiometric coefficients between one and two. The rate constant is almost unrelated to the structure of the phenol, while the number of ABTS radicals scavenged by each phenol molecule increases with para-substitution. These results are explained in terms of a fast, reversible electron transfer \documentclass{article}\pagestyle{empty}\begin{document}$$ ABTS^{\buildrel{+}\over{\cdot}}\,+PhOH {\buildrel{\longrightarrow}\over{\longleftarrow}} ABTS + PhO\bullet+H^{+} $$\end{document} followed by the self-combination of the phenoxy radicals and/or their reaction with another ABTS derived radical action. The relative rate of these processes determine the value of the stoichiometric coefficient. © 1997 John Wiley & Sons, Inc. Int J Chem Kinet 29: 219-224, 1997.
    Additional Material: 7 Ill.
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