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  • 11
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Salt effects on the oxidation of the iron(II) complexes Fe(CN)4(bpy)2-, cis-(CN)2(bpy)2 and Fe(bpy)32+ by S2O82- as well as on the reaction Fe2+ + Co(NH3)5Cl2+ have been studied in concentrated electrolyte solutions at 298.2 K. We have gone from anion-anion to cation-cation reaction with the intermediate cases of anion-neutral and cation-anion reactions. Results show that the main cause of the kinetic salt effects observed is the interaction between supporting electrolytes and the solvent. © 1994 John Wiley & Sons, Inc.
    Additional Material: 4 Ill.
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  • 12
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The electron transfer reaction [(NH3)4COIII(μ-pzCO2)FeII(CN)5]- → [(NH3)4COII(μ-pzCO2)FeIII(CN)5]- has been studied in water-cosolvent mixtures at ionic strength of I = 0.5 mol dm-3 (NaClO4). A multiparameter regression coefficients have been compared to those obtained for the same reaction to a different ionic strength (I = 2.8 10-3 mol dm-3). The magnitude of these coefficients changes with the ionic strength. An explanation is given for this behavior. © 1996 John Wiley & Sons, Inc.
    Additional Material: 1 Ill.
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  • 13
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: This paper reports a new thermal programmed desorption-mass spectrometry (TPD-MS) method for determining the number and relative strength distribution of basic sites in solid catalysts using CO2 as titrant. The overall desorbed CO2 area is proportional to the total basicity, while the number of peaks and their maximum temperature (Tmax) are related to the particular type of basic site and its strength. The activation energy for CO2 desorption from various basic sites in each catalyst was calculated via TPD-MS experiments conducted at a variable heating rate for each catalyst, using the Kissinger equation. Diffuse reflectance infrared analysis of the bands at 2000-1000 cm-1 for CO2 adsorbed on various catalysts allows one to elucidate the nature of the chemical species involved, which depends on the particular type of site. The total basicity results obtained are compared with those provided by an existing spectrophotometric method using benzoic acid (pKa=4.19) as titrant.
    Additional Material: 8 Ill.
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  • 14
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 2000 (2000), S. 1805-1813 
    ISSN: 1434-193X
    Keywords: C-Glycosides ; Conformation analysis ; Molecular dynamics ; Selectins ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---The conformational behavior of the C-glycosyl analogue of sialyl-α-(2→3)-galactose, synthesized as a glycosidase inhibitor, has been studied using a combination of NMR spectroscopy (J and NOE data) and molecular dynamics calculations. The obtained results show that the population distribution of conformers with respect to the orientation about the pseudo-glycosidic linkages is mainly controlled by steric interactions. This is in contrast to findings made for O-glycosides. In these natural compounds, the conformational behavior about the glycosidic linkage Φ is mainly governed by the exo-anomeric effect.
    Additional Material: 5 Ill.
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  • 15
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 2000 (2000), S. 1945-1952 
    ISSN: 1434-193X
    Keywords: Carbohydrates ; Glycosides ; Conformation analysis ; Molecular modeling ; Carbohydrates ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---The conformational behaviours of several nonhydrolizable lactose analogues, namely methyl α-thiolactoside (1), methyl β-carbalactoside (2) and methyl β-carbaiminolactoside (3) have been studied using a combination of NMR spectroscopy (J and NOE data) and molecular mechanics calculations. Analogies and differences with the natural compounds have been found.Supporting information for this article is available on the WWW under //http://www.wiley-vch.de/contents/jc_2046/2000/99592_s.pdf or from the author.
    Additional Material: 3 Ill.
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  • 16
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 60 (1996), S. 2041-2048 
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The thermal degradation of some plastisols [poly(vinyl chloride) and plasticizer mixtures] normally used in the toy industry was studied using a nonisothermal thermogravimetric technique. Some kinetic parameters such as activation energies are calculated according to some methods reported in the literature. A mathematical model based on considerations of the plasticizer amount was proposed to foresee the thermal degradation behavior of plastisols mostly used in the toy industry. Activation energies calculated according to the proposed model agree reasonably well with experimental results in a broad range of plastisol composition. © 1996 John Wiley & Sons, Inc.
    Additional Material: 5 Ill.
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  • 17
    Electronic Resource
    Electronic Resource
    Bognor Regis [u.a.] : Wiley-Blackwell
    ISSN: 0887-6266
    Keywords: oriented fluoro-oligomers ; chemical vapor deposition ; ferroelectricity ; glass transition ; Brillouin spectroscopy ; x-ray diffraction ; vinylidene fluoride ; trifluoroethylene ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The room temperature phase of the physical/chemical vapor-deposited statistical co-oligomer VDF/TrFE(70/30) has been characterized by different experimental methods such as small-angle x-ray scattering, wide-angle x-ray diffraction, size-exclusion chromatography, infrared absorption and optical refractometry. The characterization of the elastic properties was carried out using high-performance Brillouin spectroscopy in connection with special scattering geometries. The co-oligomer VDF/TrFE(70/30) was obtained by cracking the parent statistical copolymer and subsequently vapor depositing the shortened chains on highly oriented PTFE substrates (PIA-technique). The room temperature phase of the resulting oriented waxy crystal mats of VDF/TrFE(70/30) is predominantly ferroelectric. The physical properties are very different to those of similarly PIA-prepared n-alkanes, perfluoroalkanes, and blockfluoroalkanes. The microstructure of VDF/TrFE(70/30) is interpreted in terms of partially crystalline nano-sized structures giving rise to a marked freezing process below room temperature. © 1995 John wiley & Sons, Inc.
    Additional Material: 11 Ill.
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  • 18
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Biopolymers 25 (1986), S. 1031-1053 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Values for the thermodynamic quantities, ΔH° = 11.8 ± 2.0 Kcal/mole and ΔS° = 43.6 ± 6.0 e.u., of the 3-13 helix-coil equilibrium of isolated S-peptide (19 residue N-terminal fragment of ribonuclease A) in aqueous solution (3 m M, 1M NaCl, pD 5.4) have been determined from a joint analysis of the Thr 3γ, Ala 6β, Phe 8meta, and Phe 8para 1H chemical shift vs temperature curves (-7 to 80°C) in several aqueous-trifluorethanol mixtures. Chemical shifts in the coil and in the helix have been determined for up to 16 protons belonging to the 3-13 fragment. Thermodynamic parameters have also been determined for C-peptide (13 residue fragment) and a number of S-peptide derivatives. From the variation of the values of the thermodynamic parameters at pD 2.5, 5.4, and 8.0, a quantitation of the two helix-stabilizing side-chain interactions can be made: (1) Δ(ΔH°) ≃ 5 Kcal/mole and Δ(ΔS°) ≃ 18 e.u. for the salt bridge Glu 2- … Arg 10+ and (2) Δ(ΔH°) ≃ 3 Kcal/mole and Δ(ΔS°) = 9 e.u. for the one in which the His 12+ imidazolium group is involved, presumably a partial stacking with the Phe 8 side chain.
    Additional Material: 4 Ill.
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  • 19
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    ISSN: 1434-1948
    Keywords: Ruthenium ; Chirality ; Cyclopentadienyl complexes ; Kinetics ; Asymmetric catalysis ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Novel, functionalized, chiral Cp-ligands with S- and P-donor atoms were designed. Together with known analogues containing ether side-chains they were complexed to ruthenium for use as chiral Lewis-acid catalysts. In the ether complexes [RuCl(η5-C5H4CH2CH2OR)(PPh3)2] {R = Me, (1S)-isobornyl, (1R)-menthyl, (1R)-fenchyl} the Cp-ligand is only η5-coordinated; all attempts to provoke a bidentate, Cp/O coordination were unsuccessful. The sulfide complex [Ru{η5:η1-C5H4CH2CH2S[(1R)-neomenthyl]}(PPh3)2][OTf] contains a bidentate Cp/S-coordinated ligand, but it is unstable. The stable phosphane complex [RuCl(η5:η1-C5H4CH2CH(Me)PPh2)(PPh3)] exists as a 77:23 mixture of diastereomers containing a strongly bidentate Cp/P ligand. The diastereomers interchange, with Ru-Cl bond cleavage as the rate-determining step.Supporting information for this article is available on the WWW under http://www.wiley-vch.de/contents/jc_2005/1999/99126_s.pdf or from the author.
    Additional Material: 6 Ill.
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  • 20
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 26 (1981), S. 1511-1517 
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The hardening process of natural (Hevea brasiliensis) rubber, that takes place when this rubber is stored in dry conditions over long periods of time, has been correlated with the presence of reactive “abnormal” groups directly grafted on the polymeric chain and in the serum of the latex. In the present work, natural Hevea (HR) and Guayule (Parthenium argentatum) rubber (GR) were stored under accelerated conditions and the changes in Mooney viscosity and molecular weight measured. The results showed that while HR undergoes hardening, GR keeps its Mooney viscosity constant, as does a constant viscosity (CV) Hevea rubber. These results are explained by the absence of functional “abnormal” groups that sustain the hardening reactions.
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