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  • Articles  (12)
  • Physical Chemistry  (9)
  • Physics  (3)
  • Wiley-Blackwell  (12)
  • Wiley
  • 1
    Electronic Resource
    Electronic Resource
    Ultrasonic degradation of polyaspartates and polyglutamates (1997)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 35 (1997), S. 2379-2384 
    Details
    ISSN: 0887-6266
    Keywords: ultrasound degradation ; microwave degradation ; polyamides ; polypeptides ; polyglutamates ; polyaspartates ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: No abstract.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Rheology of rodrun liquid-crystalline polymers (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 253-263 
    Details
    ISSN: 0887-6266
    Keywords: thermotropics ; dynamic viscoelasticity ; relaxation peaks ; gelation ; crystallization ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The rheological characterization of two commercial thermotropic liquid crystalline polymers based on poly(ethylene terephthalate) (PET) and para-hydroxybenzoic acid (PHB) is carried out. The thermal transitions determined by DMTA are explained by the random character of these copolyesters, in comparison with non-random copolyesters synthesized by Jackson and Kuhfuss. The evolution of the dynamic viscoelastic functions with time in the nematic state is concave in shape for the 20%PET/80%PHB copolymer, a result that leads us to treat this system as a suspension of solid spheres (unmolten crystals) where the volume fraction of crystals increases with time according to an Avrami equation. The response of 40%PET/60%PHB copolymer is similar to a chemical or physical gelation and the hypothesis that the polydomain structure gives rise to a network is considered. Continuous flow, time-independent viscosity results reveal the existence of a three-region flow curve for 40%PET/60%PHB copolymer, but a Newtonian zone followed by a shear thinning region for 20%PET/80%PHB sample. At high temperatures the isotropization of the samples leads to a very strong decrease of the activation energy of flow, which becomes zero for 40%PET/60%PHB. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 253-263, 1998
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Classification of the solubility behaviour of β-cyclodextrin in aqueous-CO-solvent mixtures (1993)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 6 (1993), S. 651-659 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The solubility behaviour of β-cyclodextrin in aqueous mixtures was studied by determining the interactions between the co-solvent and water. Three clear classes of co-solvent are evident. In the first, including ethanol, tetrahydrofuran and acetone, there is formation of clathrate hydrates by the co-solvent. In these systems the solubilization is a maximum at the mole fraction corresponding to the minimum in the partial excess molar volume. The second class, including such solvents as dimethyl sulphoxide and pyridine, forms strong molecular complexes with water, and here a valley and a plateau region occur in the solubility values. In the third class, including formamide and urea, a steady increase in the solubility is observed. For these highly polar solvents no maxima are observed in intrinsic solvent properties such as the partial excess molar volume.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/poc.610061203
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  • 4
    Electronic Resource
    Electronic Resource
    Protonation of fully aromatic betacarbolines in highly concentrated sulphuric acid media (1995)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 8 (1995), S. 559-562 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The monocation-dication equilibria of 6-nitro and 6-sulphonic acid derivatives of betacarboline (9H-pyrido[3,4-b]indole) were investigated mostly by UV-visible absorption spectroscopy. Dications are formed in very highly concentrated sulphuric acid solutions (〉15 M). Ionization constants, pKa values and solvation parameters obtained from the excess acidity method are reported. The unusually high m* parameters are discussed and compared with other related data.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/poc.610080807
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  • 5
    Electronic Resource
    Electronic Resource
    Stepwise mechanisms of the aminolyses of 4-Nitrophenyl and 2,4-Dinitrophenyl O-Ethyl Dithiocarbonates in aqueous Ethanol (1995)
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 27 (1995), S. 987-995 
    Details
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The reactions of the title substrates with a series of secondary alicyclic amines are subjected to a kinetic study in 44 wt% aqueous ethanol, at 25.0deg;C, ionic strength 0.2 M (maintained with KCl). Pseudo-first-order kinetics are found under amine excess. The order in amine obtained is one in the reactions of all amines. The Brönsted-type plots for the overall second-order rate coefficients are biphasic with slopes β1 = 0.3 (high pKa), β2 = 0.95 (low pKa) for the aminolysis of the 4-nitro derivative, and β1 = 0.3 and β2 = 0.80 for the aminolysis of the dinitro compound; the pKa values at the curvature center are pKa0 = 9.8 and 9.5, respectively. From a comparison of these pKa0 values with those found in the same reactions in water and the shapes of the Brönsted-type plots, it is concluded that these reactions are stepwise, with the formation of a zwitterionic tetrahedral intermediate in the reaction pathway. © 1995 John Wiley & Sons, Inc.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/kin.550271004
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  • 6
    Electronic Resource
    Electronic Resource
    Influence of the side chain on the stability of Schiff-bases formed between pyridoxal 5′-phosphate and amino acids (1990)
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 22 (1990), S. 905-914 
    Details
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The stability of some Schiff-bases formed between PLP and different amino acids has been investigated in a wide range of pH. The kinetic constants of formation of these compounds and their hydrolysis rate constants have been determined. Results show that the α-position of the carboxyl group of amino acid plays an important role on the mechanism of water attack upon the C=N—bond. The absence of ionic groups in the surroundings of that bond must be an important factor of stability. Bulky hydrophobic substituents in the amino acid, near the amine part, protect the imine bond against hydrolysis.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/kin.550220903
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  • 7
    Electronic Resource
    Electronic Resource
    Schiff bases between pyridoxal 5′-phosphate and dodecylamine. Kinetic study (1992)
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 24 (1992), S. 67-78 
    Details
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We studied the formation and hydrolysis of the Schiff base of pyridoxal-5′ -phosphate (PLP) and n-dodecylamine (DOD) by kinetic methods and found the formation rate constants to be much larger than those reported for related systems. This can be ascribed to the occurrence of local concentration of charges in the vicinity of the carbinolamine, which stabilizes the corresponding transition state of the dehydration reaction. On the other hand, the hydrolysis rate constants of our system were considerably smaller as a result of the 12-atom hydrocarbon chain acting as a bulky hydrophobic rest protecting the imine bond from attack by water.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/kin.550240108
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  • 8
    Electronic Resource
    Electronic Resource
    Structural studies on the polymorphism of nylon 3 (1985)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 23 (1985), S. 733-742 
    Details
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The structure and morphology of crystalline nylon 3 [poly(β-alanine)] have been studied by electron microscopy and x-ray diffraction. Two clearly defined forms are detected. Form I appears as spherulites made up of ribbonlike lamellae upon crystallization at high temperature from a solution in phenol-butanediol-1,4. They have monoclinic unit cell with a = 9.60 Å, c = 8.96 Å, and β = 122.5°. The hydrogen-bonded planes run parallel to the long dimension of the crystals. Form II is observed when the samples are prepared from formic acid solution at room temperature. A second type of spherulite with a microfibrillar structure is formed in this case. The isolated crystalline structures obtained from Form II appear to grow along the intersheet direction rather than along the hydrogen bond direction, which constitutes anomalous behaviour. Our results for this second form are consistent with an orthorhombic lattice with a = 9.56 Å and c = 7.56 Å. No clear information is obtained on the b dimension of the unit cell (chain axis) in either case. We assume a value of 4.78 Å, which corresponds to fully extended chains. The two forms coexist in films prepared from a formic acid-water solution as well as in samples recovered immediately after polymerization.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1985.180230409
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  • 9
    Electronic Resource
    Electronic Resource
    The formation of the complex pentacyano(3-pyrazincarboxylate)ferrate(II) in various water-cosolvent mixtures (1990)
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 22 (1990), S. 1017-1026 
    Details
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: This article presents the kinetic of formation of pentacyano(3-pyrazincarboxylate)ferrate(II) from pyrazincarboxylate and pentacyanoaquoferrate(II) ions in various isodielectric water-cosolvent mixtures at 298 K. The rate law is in the form d[Fe(CN)5(3-pzCO2)4-]/dt = kf[Fe(CN)5H2O-3] [pzCO2-]. Plots of log(kf/dm3 mol-1 s-1) vs. Dm-1 (where Dm is the bulk dielectric constant of the medium) and log(kf/dm3 mol-1 s-1) vs. the Grunwald-Winstein parameter are nonlinear for some of the mixtures and to each mixture corresponds a different behavior in respect to the above parameters. The plots of log(kf/dm3 mol-1 s-1) vs. the mol fraction of water are straight lines over the entire composition range studied, except for the water-methanol mixture. It is evident that the solvation phenomenon plays a dominant role and that the rate of formation is mediated by the dual solvent vectors, the overall basicity and acidity of the solvent mixtures.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/kin.550221002
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  • 10
    Electronic Resource
    Electronic Resource
    Alkaline hydrolysis of cephaloridine: An 1H—NMR study. Temperature dependence of the rate constants (1993)
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 25 (1993), S. 865-874 
    Details
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A kinetic study on the basic hydrolysis of cephaloridine at pD= 10.5 was carried out by using the 1H—NMR technique. Epimerization at H7, a nucleophilic attack of hydroxyl ion on the β-lactam carbonyl group followed by the release of the pyridine molecule, and isomerization of the double bond at position 3 in the dihydrothiazine ring were the major reactions observed.Based on the results obtained, it should be emphasized that the presence of a pyridine group at 3′ results in a slightly increased formation constant for the exo methylene compound relative to other cephalosporins with different substituents at that position.The activation energy for the epimerization constant and the cleavage of the β-lactam ring at pD 10.5 was 21.2 kcal/mol. © 1993 John Wiley & Sons, Inc.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/kin.550251007
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