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  • Articles  (29)
  • Chemistry  (29)
  • Polymer and Materials Science  (2)
  • 1975-1979  (29)
  • 1
    Electronic Resource
    Electronic Resource
    Levans. V. Kinetics of the acid hydrolysis of Streptococcus salivarius levan (1975)
    New York : Wiley-Blackwell
    Biopolymers 14 (1975), S. 2373-2385 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The kinetics of the acid hydrolysis of Streptococcus salivarius levan were studied by examining the weight-average molecular weight. The molecular weights were obtained in a continuous manner from light scattering. Two first order reactions were observed: an initial rapid reaction in competition with a slower reaction.Activation energies, activation entropies, as well as the rate dependence upon substrate and hydrogen ion concentrations were determined. The data seem to indicate that the fast reaction is related to the breaking of branch-point bonds while the slower reaction is related to the breaking of main-chain bonds. Thus, levan hydrolysis seems to be fundamentally different from the completely random degradation of other branched polysaccharides, i.e., dextran, glycogen, and amylopectin.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1975.360141111
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  • 2
    Electronic Resource
    Electronic Resource
    Levans. II. Light-scattering and sedimentation data of Streptococcus salivarius levan in water (1975)
    New York : Wiley-Blackwell
    Biopolymers 14 (1975), S. 1283-1292 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The molecular weights and radii of gyration of Streptococcus salivarius levan fractions were obtained from light-scattering measurements in water. Sedimentation coefficients and partial specific volumes of the fractions were also obtained. Double logarithmic plots of [η] versus M̄w and S0 versus M̄w yielded slopes having values of 0.17 and 0.62, respectively. The data and various calculated parameters show that levan from Streptococcus salivarius is highly branched and behaves hydrodynamically as a compact particle of spherical symmetry.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1975.360140616
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  • 3
    Electronic Resource
    Electronic Resource
    Struktur des Silybins, III. Synthese einer 2,3-unsymmetrisch disubstituierten 2,3-Dihydro-1,4-benzodioxin-6-carbonsäure (1977)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 110 (1977), S. 3664-3671 
    Details
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Structure of Silybin, III. Synthesis of a 2,3-Unsymmetrically Disubstituted 2,3-Dihydro-1,4-benzodioxin-6-carboxylic Acidtrans-3-(3,4-Dimethoxyphenyl)-2,3-dihydro-2-(methoxymethyl)-1,4-benzodioxin-6-carboxylic acid (1a) was synthesized by an unambiguous way, and has been proved to be identical with a degradation product previously obtained from dehydrosilybin of natural origin after permethylation and alkali treatment.
    Notes: trans-3-(3,4-Dimethoxyphenyl)-2,3-dihydro-2-(methoxymethyl)-1,4-benzodioxin-6-carbonsäure (1a) wurde auf eindeutigem Wege synthetisiert und erwies sich als identisch mit dem Alkaliabbauprodukt des Dehydrosilybin-pentamethylethers.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19771101120
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  • 4
    Electronic Resource
    Electronic Resource
    2,3,6-Unsymmetrisch substituierte 2,3-Dihydro-1,4-benzodioxine: Stellung des Phenylrestes bei der Synthese nach Vorländer (1977)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 110 (1977), S. 3867-3873 
    Details
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Condensation of 1-Aryl-1,2-dibromopropane with 4-Substituted Catechols: 2-Position of the Phenyl Substituent in the 2,3,6-Unsymmetrically Substituted 2,3-Dihydro-1,4-benzodioxine MoleculeThe reaction of 4-methyl- and 4-formylcatechol with 1-aryl-1,2-dibromopropane leads to 2,3-trans-2,3,6-trisubstituted 2,3-dihydro-1,4-benzodioxine derivatives with the phenyl substituent in position 2 (1b, 2b). The structure of the reaction products is elucidated by comparing the products with those obtained by an unambiguous synthesis.
    Notes: Bei der Umsetzung von 1-substituiertem 3,4-Dihydroxybenzol mit 1-Aryl-1,2-dibrompropan wurden als einzig kristallisierbare Reaktionsprodukte 2,3-trans-2,3,6-trisubstituierte 2,3-Dihydro-1,4-benzodioxin-Derivate mit dem Phenylsubstituenten in 2-Stellung erhalten (1b, 2b). Die Konstitutionsaufklärung der Reaktionsprodukte erfolgte durch Vergleich mit auf eindeutigem Wege erhaltenen Vergleichssubstanzen.
    Additional Material: 3 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19771101217
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  • 5
    Electronic Resource
    Electronic Resource
    Der Einfluß von Wasser auf die katalytische Aktivität von Bis(π-cyclopentadienyl)titandichlorid-Dimethylaluminiumchlorid zur Polymerisation von ÄthylenIn memoriam Prof. Karl Ziegler. (1975)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1975 (1975), S. 463-469 
    Details
    ISSN: 0075-4617
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: The Effect of Water on the Catalytic Activity of Bis(π-cyclopentadienyl)titanium Dichloride-Dimethylaluminium Chloride for the Polymerization of Ethylene)The combination (C5H5)2TiCl2 -(CH3)2AlCl has little, if any, activity as a catalyst for the polymerization of ethylene. The addition of small amounts of water, ca. 0.2-0.5 mole per mole of aluminium, converts it into an extremely active catalyst. Other additives, e. g., alcohols or oxygen, do not show the same effect. The reaction is discussed.
    Notes: Die Kombination (C5H5)2TiCl2-(CH3)2AlCl hat, wenn überhaupt, nur geringe katalytische Aktivität für die Polymerisation von Äthylen. Die Zugabe geringer Mengen Wasser, ca. 0.2 -0.5 mol pro mol Aluminium, verwandelt diese Kombination in einen außerordentlich aktiven Katalysator. Andere Zusätze, z. B. Alkohole oder Sauerstoff, haben nicht die gleiche Wirkung. Der Reaktionsmechanismus wird diskutiert.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.197519750310
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  • 6
    Electronic Resource
    Electronic Resource
    Nuclear magnetic resonance of oriented molecules in lyotropic liquid crystalline media: p-cresol (1977)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 10 (1977), S. 132-134 
    Details
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Proton-proton distance ratios and order parameters for partially oriented p-cresol in a lyotropic mesophase derived from potassium laurate are obtained. The order parameters are the largest yet found for an ordered solute in a nematic-like lyotropic system. The dipolar couplings and structural data were independent of the rotational potential from 0-200 cal mol-1.
    Additional Material: 4 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1270100132
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  • 7
    Electronic Resource
    Electronic Resource
    Nuclear magnetic resonance of oriented molecules in lyotropic liquid crystalline media: Pyridine, 4-cyanopyridine and benzonitrile (1977)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 9 (1977), S. 148-150 
    Details
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Proton distance ratios for pyridine, benzonitrile and 4-cyanopyridine have been obtained in a potassium laurate lyotropic mesophase and compare favorably with values for different thermotropic solvents. Order matrices indicate a preference for the C2v symmetry axis of the molecules to be aligned along the optical axis of the mesophase.
    Additional Material: 5 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1270090308
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  • 8
    Electronic Resource
    Electronic Resource
    Quantitative analysis of a mixture of cresols by carbon-13 NMR spectroscopy (1979)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 12 (1979), S. 260-262 
    Details
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The suitability of 13C NMR as a technique for determining o-, m, and p-cresols in their mixtures was investigated. Spectra were determined in methanol, containing o-toluidine as an internal standard, without nuclear Overhauser suppression. Ratios of peak areas of each cresol isomer to o-toluidine were determined by means of the standard calibration method, and then mixtures of cresol isomers were prepared and quantified in varying concentrations from 8.30 to 66.84 mol% for each isomer, with an average absolute error of 0.78% for all isomers. The method described was convenient and the results were generally satisfactory.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1270120419
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  • 9
    Electronic Resource
    Electronic Resource
    Chemical shifts for tritons in chlorobenzene, bromobenzene, fluorobenzene and toluene as determined by tritium NMR spectroscopy (1979)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 12 (1979), S. 440-441 
    Details
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Chemical shifts for tritons in chlorobenzene have been measured in the pure compound and in a dilute solution in cyclohexane using a 64 MHz NMR spectrometer. The order of shifts is o〉m〉p. Triton shifts in pure bromobenzene, fluorobenzene and toluene have also been measured and the influence of CCl4 solvent on the aromatic triton shifts in toluene explored. Complete resolution of the three aromatic triton positions is achieved in pure toluene, but the ortho and para shifts are not resolved in 25% solution in CCl4.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1270120712
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  • 10
    Electronic Resource
    Electronic Resource
    Tritium labelling of hexamethyldisiloxane for 3H NMR referencing (1979)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 12 (1979), S. 551-552 
    Details
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Tritium labelled hexamethyldisiloxane is a suitable material for the internal referencing of 3H NMR spectra. Such a referencing procedure is necessary where the instrument is not capable of scanning 1H resonance under identical experimental conditions. Hexamethyldisiloxane may be tritiated to high activity (typically 1 Ci ml-1) by Raney nickel catalysed exchange with elemental tritium in a simple one-step procedure. A variety of heterogeneous catalysts are shown to be inactive in the common labelling method involving exchange with tritiated water.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1270120910
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