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  • Computational Chemistry and Molecular Modeling  (46)
  • Physical Chemistry  (31)
  • Wiley-Blackwell  (77)
  • American Meteorological Society (AMS)
  • PANGAEA
  • 1990-1994  (33)
  • 1980-1984  (44)
  • 1993  (33)
  • 1984  (44)
Collection
Keywords
Publisher
  • Wiley-Blackwell  (77)
  • American Meteorological Society (AMS)
  • PANGAEA
Years
  • 1990-1994  (33)
  • 1980-1984  (44)
Year
  • 1
    Electronic Resource
    Electronic Resource
    Stereochemistry of aminolysis of N-pentafluorophenylcarbonimidoyl dichloride. Crystal and molecular structures of N2-pentafluorophenyl-N1,N1-dibenzylchloroformamidine (1993)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 6 (1993), S. 319-325 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: It has been established that the product of the reaction of N-pentafluorophenylcarbonimidoyl dichloride (1) with dibenzylamine, viz. N2-pentafluorophenyl-N1,N1-dibenzylchloroformamidine (4a) is a Z-isomer, whereas according to the concept of stereoelectronic control one might have expected a product with E-configuration. The heat of formation and the geometry of Z- and E isomer of N2-pentafluorophenyl-N1,N1-diethylchloroformamidine (4b) (the latter is a product of the reaction of 1 with diethylamine) were calculated with the semi-empirical MNDO method. The calculated geometry of (Z)-4b was found to be in a good agreement with the experimentally determined structure of 4a. The formation of (Z)-4b is more preferable energetically than that of (E)-4b; the calculated difference in the heats of formation is 2·8 kcal mol-1. Thermodynamic control of the reaction stereochemistry is proposed.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/poc.610060602
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  • 2
    Electronic Resource
    Electronic Resource
    Molecular mechanics assessment of the configurational statistics of polyoxyethylene (1984)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 5 (1984), S. 241-247 
    Details
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: Previous investigators have shown that statistical mechanical averages for configuration-dependent physical properties of long unperturbed polyoxyethylene chains are sensitive to the gauche-trans energy difference for rotation about C—C bonds. Agreement between theory and experiment could be obtained only by significant adjustment of this energy away from values predicted by semiempirical conformational energy computations. The present work examines the success of MM2 in evaluating conformational properties of long unperturbed polyoxyethylene chains. Calculations are performed which identify the rotational isomers, and their energies, for the indicated bonds in CH3OCH2CH2O—CH2—CH2—OCH2CH2OCH3. These energies are used to assign statistical weights utilized in the configuration partition function for a rotational isomeric state chain with symmetric threefold interdependent rotations. The customary generator matrix scheme is employed to evaluate the mean-square unperturbed end-to-end distance, mean-square unperturbed dipole moment, and their temperature coefficients. Contrary to computational schemes employed previously, MM2 is found to provide an estimate of the gauche-trans energy difference for rotation about C—C which is in harmony with the known dimensions and dipole moments of the unperturbed polymer. MM2 also provides good estimates for most of the other parameters required in the rotational isomeric state treatment. A notable exception is provided by the gauche-trans energy difference for rotation about the C—O bond. This energy difference is overestimated by MM2.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcc.540050306
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  • 3
    Electronic Resource
    Electronic Resource
    On searching neighbors in computer simulations of macromolecular systems (1984)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 5 (1984), S. 272-279 
    Details
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: Various algorithms for evaluating nonbonded interactions in molecular dynamics (MD) simulations of macromolecular systems are considered, and a combination of two techniques using a space grid for finding neighbor atoms is proposed. The application of grid search techniques to nonrectangular periodic systems is discussed. Finally, the computing time required by different algorithms is compared on a Cray-1 vector processing computer as well as on a CDC Cyber 170/760 sequential computer. Neighbor list techniques turn out to be faster than the grid search techniques for the systems considered here. However, storage requirements may exclude the use of neighbor list techniques for large systems. Finally, MD of complex macromolecular systems turned out to be about 4-14 times faster on a Cray-1 than on a Cyber 170/760.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcc.540050311
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  • 4
    Electronic Resource
    Electronic Resource
    Basic hydrolysis of glyceryl nitrate esters. III. Trinitroglycerin (1984)
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 16 (1984), S. 1027-1051 
    Details
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Kinetics of the basic hydrolysis of glyceryl trinitrate (TNG) were investigated in CO2-free aqueous calcium hydroxide solutions. The hydrolysis reactions were carried out in a temperature controlled reactor vessel with provision for continuous N2 sparging of the reaction mixture. TNG hydrolyzed via second-order reaction at 25°C, 18°C, and 10°C. The activation energy of the hydrolysis reaction of TNG was calculated from the kinetic data and found to be equal to 27.53 kcal/mol. The major products of the hydrolysis of TNG in solution of calcium hydroxide were calcium nitrate and calcium nitrite, accounting for approximately 50% of the degradation products. The minor identified products such as calcium oxalate and nitrate esters amounted to approximatey 6% of the products. The remaining 30% of the isolated products was a mixture of calcium formate, a nitrate ester, and unidentified volatiles, polymerlike substances, and other organic residue.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/kin.550160808
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  • 5
    Electronic Resource
    Electronic Resource
    Thermal decomposition of methyl nitrite in shock waves studied by laser probing (1984)
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 16 (1984), S. 1139-1150 
    Details
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The unimolecular decomposition of methyl nitrite in the temperature range 680-955 K and pressure range 0.64 to 2.0 atm has been studied in shock-tube experiments employing real-time absorption of CW CO laser radiation by the NO product. Computer kinetic modeling using a set of 23 reactions shows that NO product is relatively unreactive. Its initial rate of production can be used to yield directly the unimolecular rate constant, which in the fall-off region, can be represented by the second-order rate coefficient in the Arrhenius form: \documentclass{article}\pagestyle{empty}\begin{document}$$k_1 = 10^{17.90 \pm 0.21} \exp (- 17200 \pm 400/T){\rm cm}^{\rm 3} {\rm mol}^{ - 1} {\rm s}^{ - 1}$$\end{document} A RRKM model calculation, assuming a loose CH3ONO≠ complex with two degrees of free internal rotation, gives good agreement with the experimental rate constants.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/kin.550160909
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  • 6
    Electronic Resource
    Electronic Resource
    Critical comparison of the ab initio and spectroscopic methyl-C—H bond length difference in acetyl compounds, CH3C(=O) XArticle no. 35 in the series Ab Initio Studies of Structural Features Not Easily Amenable to Experiment. (1984)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 5 (1984), S. 517-522 
    Details
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: In order to provide additional data for the relative lengths of methyl-C—H bond distances in acetyl derivatives, which are difficult to determine accurately by the conventional tools of structural chemistry, the geometries of CH3COH, CH3COF, CH3COCH3, CH3COOH, and CH3CONH2 were determined by ab initio SCF gradient optimization at the 5-31G** level and compared with previous 4-21G results. For acetaldehyde 6-311G4* calculations were also performed and the correlated methyl-C—H stretching potential energy functions were determined. It is found that the calculated differences between the in-plane and out-of-plane methyl-C—H bonds are practically independent of the computational scheme. The calculated results are in contrast to relative bond lengths obtained by some vibrational overtone spectroscopic studies, but are in perfect agreement with C—H bond length differences determined from isolated C—H stretching frequencies of partially deuterated compounds. The reliability of the latter, and other spectroscopic data concerning the assignment of the methyl-C—H vibrations are critically analyzed. On the basis of the available evidence we conclude: (1) the methyl groups of the CH3C(=O)X systems here discussed contain one strong (in-plane) and two weak (out-of-plane) C—H bonds; (2) intensities of C—H local mode spectra do not provide a reliable basis for assignment to individual bonds.
    Additional Material: 4 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcc.540050603
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  • 7
    Electronic Resource
    Electronic Resource
    Application of an ion-fitted pseudopotential to HF, H2O, NH3, BeO, and HCl in a Gaussian lobe basisFrom the thesis of T. T. Nguyen. (1984)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 5 (1984), S. 640-649 
    Details
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: The core potentials for atoms of atomic numer 1-18 fitted to ion spectra by Chang, Habitz, Pittel, and Schwarz have been extended to the molecular case in a Gaussian lobe basis by using a six-Gaussian (6G-POT) representation for the exponential factors of the atomic core potentials. In a (9s/5p/1d) basis the 6G-POT one-electron energies, dipole moments, and Mulliken charges are improved over a one-Gaussian potential form for HF, NH3, and H2O; BeO also yields good agreement within 2.6% of the experimental bond length. For HCl, the core potential shows larger errors in the dipole moment (7%) and one-electron eigenvalues (2%), but a 75% saving in computer time is realized for HCl compared with only about 35% for first-row systems using the 6G-POT core potentials. Analytical expressions are given to extend the 6G-POT method up to s, p, d, f, and g valence shells.
    Additional Material: 9 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcc.540050618
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  • 8
    Electronic Resource
    Electronic Resource
    Basic hydrolysis of glyceryl nitrate esters. II. 1,2-glyceryl and 1, 3-glyceryl dinitrate esters (1984)
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 16 (1984), S. 1009-1026 
    Details
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Kinetics of the basic hydrolysis of 1,2-glyceryl dinitrate (1,2-DNG) and 1,3-glyceryl dinitrate (1,3-DNG) esters were investigated in CO2-free aqueous calcium hydroxide solutions. The hydrolysis reactions were carried out in a temperature controlled reactor vessel with provision for continuous N2 sparging of the reaction mixture. Both glyceryl dinitrate esters hydrolyzed via second-order reaction at 25°C. 1,2-DNG in basic solutions isomerized to 1,3-DNG which subsequently hydrolyzed to yield products. The main hydrolysis product of 1,3-DNG was identified as glycidyl nitrate. Other products formed during the basic hydrolysis of DNGs were nitrites and nitrates.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/kin.550160807
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  • 9
    Electronic Resource
    Electronic Resource
    Yields of singlet nitrenes from halogen atom - azide molecule reactions (1984)
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 16 (1984), S. 977-993 
    Details
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Chemiluminescence from the a1Δ and b1Σ+ excited electronic states of nitrogen halide diatomics is observed when HN3 is allowed to react with mixtures of halogen atoms in a discharge-flow apparatus. Excited NF (a1Δ) is produced by the F + HN3 reaction, and NCl (a1Δ, b1Σ+) and NBr (a1Δ, b1Σ+) are produced by the F, Cl, + HN3 and F, Br + HN3 reactions, respectively. In the low-density limit, the yield of NF(a1Δ) was found to be near unity. The yields of the b1Σ+ states of NCl and NBr were determined to have a lower limit of ca. 10%. A number of results from these experiments, including direct observation of N3 radicals in the flow, support a hypothetical mechanism in which N3 acts as an intermediate. A second possible mechanism proceeding via an HNF intermediate cannot be ruled out.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/kin.550160805
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  • 10
    Electronic Resource
    Electronic Resource
    A study of ethane decomposition in a shock tube using laser absorption of CH3 (1993)
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 25 (1993), S. 969-982 
    Details
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The rate coefficient for the unimolecular reaction, C2H6 → CH3 + CH3, was measured in reflected shock wave experiments using narrow-linewidth laser absorption of methyl radicals at 216.6 nm. The experiments were conducted in the falloff regime at the conditions 1350 to 2110 K, 0.58 to 4.4 atm, in 50 to 500 ppm C2H6/Ar and 190 ppm C2H6/N2 mixtures. At temperatures below 1500 K, the measured rate coefficients are in good agreement with the expression of Wagner and Wardlaw (1989). Above 1500 K, the measurements fall increasingly below their predictions. © 1993 John Wiley & Sons, Inc.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/kin.550251109
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