ALBERT

All Library Books, journals and Electronic Records Telegrafenberg

X
feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
Filter
  • Theoretical, Physical and Computational Chemistry  (7)
  • Wiley-Blackwell  (7)
  • 1
    Electronic Resource
    Electronic Resource
    Conductivity in polyacetylene. IV. Ab initio calculations for a two-site model for electron transfer between allyl anion and allyl (1997)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 61 (1997), S. 847-857 
    Details
    ISSN: 0020-7608
    Keywords: Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Electron exchange between allyl molecules is studied using quantum chemical ab initio methods in order to model interchain electron transfer (ET) in polyacetylene. The reaction path, reorganization energy for ET (λ), and the electronic factor (Δ) are calculated using the UMP2, CASSCF, CASPT2, and CASSI methods. Changes in bond lengths are very small and their contribution to the internal reorganization energy almost negligible. Only changes in the bond angle leave significant contributions to the reorganization energy. The calculated potential energy surfaces can be represented as interacting parabolic-well potentials only in the case of CASSI. The UMP2, CASSCF, and CASPT2 methods give the localization of the electron even in the symmetric case and incorrect energy surfaces, with a cusp at the symmetry point. The electronic factor Δ is calculated using the two different methods, Koopmans' theorem and CASSI, with the same basis set. They are quantitatively very close for all intermolecular distances under study. However, Δ is sensitive to the basis set and cannot be calculated accurately in the present case. © 1997 John Wiley & Sons, Inc.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
  • 2
    Electronic Resource
    Electronic Resource
    Gas-phase thermolysis of N-substituted diallyl- and allylpropargylamines (1997)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 10 (1997), S. 49-54 
    Details
    ISSN: 0894-3230
    Keywords: Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: ---Various diallyl- and allylpropargylamines were pyrolyzed in a stirred-flow reactor at temperatures in the range of 330-500°C, pressures of 8-16 Torr and residence times of 0·4-2·4 s using toluene as carrier gas. The reaction products were propene, allene and aldimines. The allene to propene ratio changed considerably with the third substituent on the N atom. At conversions in the range 13-55%, the consumption of the amines showed first-order kinetics. The following Arrhenius parameters [A (s-1) and Ea (kJ mol-1)] were obtained from the rate coefficients: diallyl-tert-butylamine, log  A = 10·32 ± 0·12, Ea = 139 ± 2; diallylneopentylamine, log A = 12·87 ± 0·26, Ea = 168 ± 3; allylpropargyl-tert-butylamine, log A = 10·23 ± 0·18, Ea = 126 ± 2; allylpropargyltosylamine, log A = 13·05 ± 0.36, Ea = 197 ± 5; and allylpropargylphenylamine, log A = 12·10 ± 0·35, Ea = 162 ± 4. Polar, six-center cyclic transition states are suggested for the elimination of propene and allene, via non-concerted bond breaking-bond forming mechanisms. © 1997 John Wiley & Sons, Ltd.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
  • 3
    Electronic Resource
    Electronic Resource
    Gas-phase thermolysis of N-methyl-N-phenyl-tert-butylsulfenamide and morpholinyl-tert-butylsulfenamide (1998)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 11 (1998), S. 407-410 
    Details
    ISSN: 0894-3230
    Keywords: gas-phase thermolysis ; N-methyl-N-phenyl-tert-butylsulfenamide ; morpholinyl-tert-butylsulfenamide ; Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: N-Methyl-N-phenyl-tert-butylsulfenamide (MPSA) and morpholinyl-tert-butylsulfenamide (MOSA) were thermolyzed in a stirred-flow reactor at temperatures of 340-390 °C and pressures of 7-13 Torr, using toluene as carrier gas, at residence times of 0.3-1.3 s. Isobutene was formed in 99% yield through first-order reactions having the following Arrhenius parameters (A,s-1, Ea, kJ mol-1): MPSA, log A  =  12.41 ± 0.02, Ea  =  158.8 ± 0.2; MOSA, log A  =  12.91 ± 0.22, Ea  =  159 ± 3. It is proposed that the elimination of isobutene takes place by unimolecular reaction mechanisms involving polar, four-center cyclic transition states, forming S-unsubstituted thiohydroxylamines as co-products. Thermochemical parameters, estimated by semiempirical AM1 calculations, are reported for the latter and for the parent molecules. © 1998 John Wiley & Sons, Ltd.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
  • 4
    Electronic Resource
    Electronic Resource
    Kinetic study of the oxidation of propan-1-ol by alkaline hexacyanoferrate(III) catalysed by ruthenium trichloride (1997)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 10 (1997), S. 662-668 
    Details
    ISSN: 0894-3230
    Keywords: propan-1-ol oxidation ; alkaline hexacyanoferrate(III) ; ruthenium trichloride catalyst ; kinetic ; Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: ---The oxidation kinetics of propan-1-ol by alkaline hexacyanoferrate(III) catalyzed by ruthenium trichloride were studied spectrophotometrically. The initial rate method was used for kinetic analysis. The reaction rate shows a fractional order in [oxidant] and [substrate] and a first-order dependence on [RuCl3]. The dependence on [OH-] is complicated. A reaction mechanism involving two active catalytic species is proposed. Each one of these species forms an intermediate complex with the substrate. The attack of these complexes by hexacyanoferrate(III) in rate-determining step produces a radical species which is further oxidized in the subsequent step. © 1997 John Wiley & Sons, Ltd.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
  • 5
    Electronic Resource
    Electronic Resource
    Reversible electrochemical reactions in conducting polymers: A molecular approach to artificial muscles (1996)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 9 (1996), S. 381-386 
    Details
    ISSN: 0894-3230
    Keywords: Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Electrical currents trigger oxidation or reduction reactions in conducting polymers. Changes in volume associated with these redox processes can be transformed into macroscopic movements of more than 180° by the construction of a bilayer: polypyrrole-flexible and inactive polymer (artificial muscle). The effects of the applied potential, the nature of the solvent and the electrolyte concentration on the angular movement of the free end of the bilayer were analysed. The movement accelerates with increasing anodic (or cathodic, when the movement is reversed) overpotentials, with increasing electrolyte concentration or by using more polar solvents, leading to the conclusion that the movement is linked to electrochemically driven exchange of hydrated counterions between the solution and the conducting polymer. Geometrical considerations give a simple equation for both the microscopic and macroscopic changes of volume associated to the penetration of counterions during oxidation, which is able to explain the experimental behaviour.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
  • 6
    Electronic Resource
    Electronic Resource
    Conductivity in polyacetylene. VI. Semiconductor - Metal transition of alkali-doped polymer (1997)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 63 (1997), S. 655-665 
    Details
    ISSN: 0020-7608
    Keywords: polyacetylene ; alkali-doped ; spectrum ; calculation ; semiconductor-metal transition ; Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A local model is set up for the conductivity in alkali-doped polyacetylene (PA) based on results of ab initio and semiempirical calculations. At low doping levels, solitons and polarons appear naturally in the (nondegenerate) ground state. Alkali atoms donate their valence electrons to neutral solitons, which have the highest electron affinity in the PA structure. Due to the high polarizability of the PA chains, there is a charge buildup on a few carbon atoms close to the alkali ion. At the same time, a new soliton, screened from the alkali ion, is formed some distance away from the latter. This solition may migrate through the PA polymer partly by hopping for one chain segment to another (Ea ≥ 0.15 eV) and partly by soliton motion. In the calculation of the spectra, we used geometry-optimized structures and configuration interaction (i.e., taking into account electron-lattice interaction and explicit Coulomb correlation) and obtained good agreement with experimental spectra. As the concentration of alkali is increased, absorption occurs at energies below 1 eV. At higher doping levels, corresponding to a few mol%, the electrons delocalize over many alkali spacings and the trapping capability of the polymer decreases the conductivity becomes bandlike. © 1997 John Wiley & Sons, Inc. Int J Quant Chem 63: 655-665, 1997
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
  • 7
    Electronic Resource
    Electronic Resource
    Role of π stabilization in cyclic polyenes (1998)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 67 (1998), S. 107-113 
    Details
    ISSN: 0020-7608
    Keywords: Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The Hückel model with bond-length-dependent coupling (β), contrary to the original Hückel model with a constant β, may be parametrized to give C-C bond lengths and some other properties in good agreement with accurate ab initio results. The paradox in seemingly contradictory conclusions of some recent works on whether the π electrons promote equal bond lengths or bond alternation in benzene is discussed for the more general group of cyclic polyenes. We find that π electrons promote bond alternation but that the interaction between π electrons of different bonds always leads to a decrease of the bond length alternation in cyclic systems (except C4H4) compared to the difference in bond length between pure single and double bonds.   © 1998 John Wiley & Sons, Inc. Int J Quant Chem 67: 107-113, 1998
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...