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  • Physical Chemistry  (27)
  • Computational Chemistry and Molecular Modeling  (10)
  • Wiley-Blackwell  (37)
  • 1
    Electronic Resource
    Electronic Resource
    Quantum-chemical study of the relation between electronic structure and pA2 in a series of 5-substituted tryptamines (1985)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 28 (1985), S. 421-428 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We have analyzed the dependence of the serotonin receptor binding affinity on the electronic and steric reactivity indexes for a group of 5-substituted tryptamines. The approaches employed are a new nonempirical Quantitative Structure - Activity relationship approach and multiple regression analyses. The results suggest that the variation of the receptor binding affinity in 5-substituted tryptamines is related to the variation of the net charge of two atoms and to the steric bulk of the N-substituent. A receptor model is proposed.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560280402
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  • 2
    Electronic Resource
    Electronic Resource
    Solution of the integral Dirac equation in momentum space (1987)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 32 (1987), S. 417-423 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We discuss the solution of the integral Dirac-Fock equation in momentum space. “Balanced” momentum-space gaussian functions are used to expand the large and small components of the Dirac 4-spinors. We show that this approach, which has been successfully used in atomic Dirac-Fock calculations, works equally well in molecular Dirac-Fock calculations.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560320741
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  • 3
    Electronic Resource
    Electronic Resource
    Fully numerical solutions of the hartree-fock equation in momentum space: A numerical study of the He atom and H+2 ion (1988)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 34 (1988), S. 445-456 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A major impediment to achieving accurate solutions of the momentum-space Hartree-Fock equation in fully numerical form lies in the error caused by the truncation of momentum space. We use a coordinate transformation, which is characterized by P = tan(α/2), thus avoiding this truncation to achieve accurate solutions of the Hartree-Fock equation. Using this approach, we have re-examined the He model problem previously analyzed by Delhalle and Defranceschi [Intern. J. Quantum Chem. Symp. 21 425 (1987)]: The kinetic, nuclear attraction and Coulomb repulsion energies of the He atom have been evaluated using both conventional spherical polar momentum coordinates, (p, θ, ϕ) and the transformed coordinates, (α,θ,ϕ) in order to compare their accuracies. We have performed a number of fully numerical calculations on the H+2 ion in order to examine the influence of the number of points in the mesh on the accuracy of the computed total electronic energy of the diatomic molecule.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560340848
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  • 4
    Electronic Resource
    Electronic Resource
    Solution of the time-dependent Schrödinger equation using a continuous Fourier transform (1991)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 40 (1991), S. 107-111 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We discuss the solution of the time-dependent Schrödinger equation. The split operator method is used to propagate an initial wave function and the continuous Fourier transform is applied to obtain the energy eigenvalues. High resolution in the energy is obtained without line shaping techniques.s
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560400813
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  • 5
    Electronic Resource
    Electronic Resource
    Kinetic study of the formation and rupture of stable tetrahedral intermediates. C—O, C—N and C—S bond formation (1994)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 7 (1994), S. 80-89 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Measured pseudo-first-order rate constants for intramolecular formation of tetrahedral intermediates from N-2-hydroxyethylphthalimide, N-2-aminoethylphthalimide and N-2-thioethylphthalimide at pH 〉 6 are reported. The reaction is specific and general base catalysed, with β(Brønsted) values 0·44, 0·52 and 0·52 respectively. From a plot of log kb (general base rate constants) vs γ′ [the affinities of EtXH (X = O, NH, S) toward the carbonylic carbon], β′nuc values of 0·01 (with OH- as specific base), 0·25 (with imdidazole as general base) and 0·27 (with HPO42- as general base were obtained). The observed relationships pxy = ϑβ′/ - ϑpKa = -ϑ(Brønsted)/ϑγ′ = 0·03 is supported by the predictions of an energy contour diagram, which, on extrapolation to a non-stable tetrahedral intermediate, predicts a late and slightly protonated transition state for the cleavage process. At pH 〈 3, these intermediates cleave to yield only the corresponding diacylimides. These reactions are general base and acid catalysed with β 〉 0·3 and α 〈 0·1. A fast equilibrium between the intermediate and its N-protonated (amide) form is reached. The general base rupture of the latter is faster than that of the corresponding non-protonated intermediate by a factor of ca 109 - 1010-fold.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/poc.610070205
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  • 6
    Electronic Resource
    Electronic Resource
    Gas phase thermolysis of N-(tert-butylthio)allylamine and N-(tert-butylthio)diethylamine (1994)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 7 (1994), S. 585-590 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The title sulphenamides were pyrolysed in a stirred-flow reactor at temperatures of 310-410°C, pressures of 8-15 Torr and residence times of 0·4-2 s using toluene as the carrier gas. N-(tert-Butylthio)allylamine formed 73 ± 4% isobutene, 23 ± 3% propene and N-allylthiohydroxylamine. The first-order rate coefficients for the formation of isobutene and propene, respectively, followed the Arrhenius equations kC4(s-1) = 1012·52 ± 0·36 exp(-163 ± 5 kJ mol-1 RT) and kC3(s-1) = 1010·99 ± 0·29 exp(-151 ± 4 kJ mol-1 RT) N-(tert-Butylthio)diethylamine gave 97 ± 1% isobutene, 1·9 ± 0·4% isobutane and N,N-diethylthiohydroxylamine. The first-order rate coefficients for isobutene elimination followed the Arrhenius equation k(s-1) = 1013·45 ± 0·24 exp(-164 ± 3 kJ mol-1 RT). The formation of the products is interpreted in terms of an elimination reaction with a unimolecular, four-centered, cyclic transition state. The reactivity of these sulphenamides was found to be much higher than that of previously studied alkyl or aryl tert-butyl sulphides and disulphides.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/poc.610071102
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  • 7
    Electronic Resource
    Electronic Resource
    Metal ion complexation by tetraester derivatives of bridged calix [4] arenes (1992)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 5 (1992), S. 471-481 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A series of bridged calix [4] arenes (5-10 methylene groups in the bridge) were synthesized and transformed into their tetraester derivatives by reaction with ethyl bromoacetate. The stability constants for complexes of the tetraester derivatives with sodium, potassium and silver cations, determined in methanol by spectroscopic or potentiometric techniques, show a drastic decrease (more than 105 for Na +) for the shorter methylene chains. 1H NMR studies demonstrate a conformational rearrangement of the calixarene part to fourfold symmetry to be necessary for the complexation of a cation, which is prevented by the shorter chains. This is further confirmed by the X-ray structure of a tetraester derivative with a CH2CH2COCH2CH2 bridge; crystals were monoclinic, space group P21/c,a = 11.847(2), b = 39.773(5), c = 12 · 127(2) Å, β = 109.24(1), V = 5395.1 Å3, Z = 4, Dx = 1.186 Mg m-3.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/poc.610050809
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  • 8
    Electronic Resource
    Electronic Resource
    Correlation and pairing in C602n- ions. Superconductivity of alkali and alkaline earth compounds of C60 (1993)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 48 (1993), S. 655-665 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Hopping conductivity becomes activationless (metallic) when twice the intersite coupling supercedes the reorganization energy. Consistent with this idea, activationless electron pair transfer may be considered as a condition for the appearance of superconductivity. For electron pairs the condition is slightly more complicated than for single electrons. The activation energy depends on the relative energies between ionic states and a valence bond state. The latter serves as an intermediate state, contributing to the disappearance of the activation barrier. In A3C60, that pairing occurs because the 1Ag state of the negative ions C602- and C604- is stabilized by correlation effects and is the ground state. The correlation effects are primarily due to the closeness in energy and different parity of the tlu and tlg orbitals, which are partly occupied in the negative ions, but empty in neutral C60. The small interelectronic repulsion and the polarization energy from the environment also contribute to the stability of the evenly negative ions. © 1993 John Wiley & Sons, Inc.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560480859
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  • 9
    Electronic Resource
    Electronic Resource
    Conductivity in polyacetylene. II. Ab initio and tight-binding calculations of soliton structure and reorganization energy in ordered and disordered structures (1996)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 58 (1996), S. 517-532 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Alkali-doped polyacetylene is considered as an electron-transfer system. To estimate the reorganization energy due to bond-length changes when electrons are added or subtracted, we applied the (U)MP2 and CASSCF methods to small systems of the type H(CH)NH. The simple tight-binding (Hückel) model with bond-length-dependent resonance integrals has been applied to the same and larger polyenes. The bond lengths are obtained via the bond orders for the various oxidation states. The results agree very well with the ab initio results and experiments for small polyenes. Odd-N and even-N systems behave differently. In odd-N systems, a structural “soliton” exists in the neutral molecule. An electron can be added or removed without bond-length change. In even-N chains, with perfect bond alternation in the neutral molecule, the bond length changes when an electron is accepted occur over about 20 carbon atoms. The reorganization energy tends to a constant value (0.22 eV) as the chain length is increased. Soliton structure is studied as a function of out-of-plane torsional defects and it is found that an additional electron is localized primarily on a segment with an odd number of carbon atoms. In the presence of positively charged ions, electrons are attracted toward this charge and positive solitons formed at some distance from the perturbing ion. © 1996 John Wiley & Sons, Inc.
    Additional Material: 8 Ill.
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  • 10
    Electronic Resource
    Electronic Resource
    Kinetics and mechanisms of the permanganate oxidation of L-valine in neutral aqueous solutions (1989)
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 21 (1989), S. 71-81 
    Details
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The permanganate oxidation of L-valine has been studied by visible spectrophotometry in neutral aqueous solutions. Under these conditions, both the zwitterionic and anionic forms of the amino acid are oxidized, the reaction being autocatalyzed by soluble colloidal manganese dioxide. Kinetic data for both the uncatalyzed and autocatalytic reaction pathways have been obtained, and reaction sequences consistent with the experimental findings are proposed.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/kin.550210202
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