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  • 1
    Electronic Resource
    Electronic Resource
    Geometrical distortion caused by substituents. 5. Method of evaluating explicative hypotheses for constrained systems (1992)
    s.l. : American Chemical Society
    The @journal of physical chemistry 〈Washington, DC〉 96 (1992), S. 6624-6629 
    Details
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/j100195a021
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    A theoretical study of 1-amino-3-butene and 3-butene-1-thiol (1992)
    Springer
    Structural chemistry 3 (1992), S. 225-229 
    Details
    ISSN: 1572-9001
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Conformational analysis of 1-amino-3-butene and 3-butene-1-thiol was carried out using the 4-21G basis set. The conformers obtained were subjected to 6-31G* single-point analysis for the calculation of energies, charge distributions, and dipole moments. The geometries and stabilities obtained are in good agreement with available experimental data. The results are interpreted in terms of intramolecular hydrogen bonding and anomeric interactions: Some of the most stable conformers of both molecules have intramolecular hydrogen bonds between the hydrogens of the amino or thiol groups and theπ electrons of the double bond. The 4-21G geometries were refined to obtain rotational constants closer to the experimental values.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00672789
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  • 3
    Electronic Resource
    Electronic Resource
    Ab initio study of the structure and tautomerism of internally hydrogen-bonded aromatic carbonyls: Salicylamide, salicylic Acid, and O-hydroxybenzoyl cyanide (1992)
    Springer
    Structural chemistry 3 (1992), S. 381-387 
    Details
    ISSN: 1572-9001
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract We carried out an ab initio study at the 3–21 G level with full geometric optimization of three compounds with intramolecular hydrogen bonds in their most stable conformations, namely salicylamide, salicylic acid, ando-hydroxybenzoyl cyanide. The energy of the hydrogen bonds was estimated and their structural effects were analyzed. We also studied the stability of the tautomers resulting from a proton transfer between the oxygen atoms by analyzing the potential surfaces of the tautomerization process. The potential surfaces of salicylamide and salicylic acid showed a single minimum, while that of the cyanide showed a double minimum with a scarcely significant inverse barrier (3.01 kJ/mol). Single point calculations at the 6–31+G* level on salicylic acid showed a trend to appear a second minimum in the potential surface. Both the strength of the hydrogen bond and the occurrence of stable tautomers were found to be clearly correlated with the electron-releasing and electron-withdrawing ability of the organic functions present in each compound (-NH2,-OH and -CN, respectively).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00672012
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  • 4
    Electronic Resource
    Electronic Resource
    Ab initio study of the structure and tautomerism of internally hydrogen-bonded aromatic carbonyls: Salicylaldehyde and o-hydroxyacetophenone (1991)
    Springer
    Structural chemistry 2 (1991), S. 575-580 
    Details
    ISSN: 1572-9001
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract We carried out an ab initio study on salicylaldehyde ando-hydroxyacetophenone with full optimization at the 3–21G level. The most stable conformation of the two compounds was that including an intramolecular hydrogen bond, the energy and structural effects of which were estimated. We also studied the stability of the respective tautomers arising from a proton transfer. Such tautomers are quinoid in nature, which implies the loss of the aromatic character of the benzene ring and hence leads to major destabilization. Thus, the tautomerization potential curve of salicylaldehyde featured an inverse barrier of only 2.1 kJ/mol; this barrier was not even present ino-hydroxyacetophenone owing to the effect of the methyl group, which thus overcome the low stability of the quinoid tautomer. In this tautomerization study some single-point calculations at the 6–31G** level were also carried out. In both compounds these calculations give rise to an increase of barriers.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00673440
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  • 5
    Electronic Resource
    Electronic Resource
    Conformation and charge distribution of bicyclic β-lactams: Structure-activity relationships (1992)
    New York : Wiley-Blackwell
    Biopolymers 32 (1992), S. 97-106 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The structures of 7-oxo-1-azabicyclo[3.2.0] heptane and its 4-oxa, 3-ethylene-4-oxa, and 3-ethylene-6-methyl-4-oxa derivatives, and of 8-oxo-1-azabicyclo[4.2.0] octane and its 5-oxa derivative, were studied by ab initio methods. Conformations were refined without constraints using the 4-21G and the 4-21G* basis sets, and energies and charge distributions were improved by single-point 6-31G*/4-21G* calculations. The results are interpreted in terms of structural trends related to β-lactamase inhibitor capability.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360320112
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  • 6
    Electronic Resource
    Electronic Resource
    Theoretical study of some nitriles: Intramolecular hydrogen bonds and anomeric effect (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 13 (1992), S. 722-729 
    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: An ab initio study of 3-chloro-, 3-hydroxy-, 3-mercapto-, and 3-amino-propanenitrile and 4-chloro-bu- tanenitrile was carried out at several levels of theory. The calculated stabilities and geometrical trends are interpreted in terms of the effects of intramolecular hydrogen bonds and anomeric interactions, and compared with available experimental data.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcc.540130607
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  • 7
    Electronic Resource
    Electronic Resource
    Semiempirical study of compounds with O-H—O intramolecular hydrogen bond (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 13 (1992), S. 860-866 
    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: Application of MNDO, AM1, PM3, MNDO/H, and MNDO/M methods to a set of compounds with intramolecular hydrogen bonds suggested that none of these methods accurately modeled the characteristics of the hydrogen bonds. Since the MNDO/H and MNDO/M methods work well for intermolecular hydrogen bonds, we followed their example and modified MNDO for intramolecular hydrogen bonds by altering the empirical core-core repulsion energy function for all pairs of atoms involved in intramolecular O-H—O bonds. The resulting modified method models the behavior of these bonds quite well, especially as regards their geometry and the barrier to proton transfer. © 1992 by John Wiley & Sons, Inc.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcc.540130710
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  • 8
    Electronic Resource
    Electronic Resource
    Parametrization of a force field for studying some beta-lactams (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 15 (1994), S. 455-465 
    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: A molecular mechanics force field for studying some beta-lactams was developed from ab initio and experimental data. The optimized parameters allowed accurate calculation of the geometries of both the compounds on which the parametrization was based and others on which the validity of the predictions was checked. © 1994 by John Wiley & Sons, Inc.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcc.540150409
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  • 9
    Electronic Resource
    Electronic Resource
    Molecular mechanics study of conformational trends in simple alcohols and ethers. II. Intramolecular hydrogen bonding (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 13 (1992), S. 851-859 
    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 this article we present an extension of our modified MM2(80) force field MM2MOD in which a potential function for hydrogen bonding in alcohols and ethers is included. The results of applying MM2(85), MM2(87), and MM2MOD on ethylene glycol, 2-methoxyethanol and 1,3-propanediol are reported and compared with available experimental data and ab initio results. It is concluded that hydrogen bonding plays an important role in determining the molecular conformations of these systems. © 1992 by John Wiley & Sons, Inc.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcc.540130709
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  • 10
    Electronic Resource
    Electronic Resource
    A molecular mechanics study of conformational trends in simple alcohols and ethers. Part I: Geometric trends (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 12 (1991), S. 872-879 
    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: We have modified the MM2(80) molecular mechanics force field for alcohols and ethers to reproduce geometric trends predicted by ab initio calculations with the 4-21G basis set. The results obtained with the modified force field are consistent with experimental evidence.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcc.540120713
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