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  • 1
    Electronic Resource
    Electronic Resource
    Theoretical studies on quinones I. The structure of p-benzoquinone and two of its excited triplet states (1988)
    Springer
    Theoretical chemistry accounts 74 (1988), S. 195-208 
    Details
    ISSN: 1432-2234
    Keywords: p-Benzoquinone ; Triplet ; Geometry ; Optimisation ; Ab initio
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Ab initio calculations on the ground and two excited triplet states (3B1g and 3B1u) of p-benzoquinone are described. The geometries of the three states were fully optimised at the SCF level using the 3-21G basis set. For the excited states, both D2h and C2v geometries were investigated. Comparison was made between UHF and ROHF levels of theory.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00527143
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  • 2
    Electronic Resource
    Electronic Resource
    Ab-initio molecular orbital studies on a new mechanism for the interconversion of monomethylnitrosamine and methyldiazohydroxide (1986)
    Springer
    Theoretical chemistry accounts 70 (1986), S. 421-427 
    Details
    ISSN: 1432-2234
    Keywords: Molecular orbital ; Nitrosamine metabolism ; Monomethyl nitrosamine ; Methyldiazohydroxide ; Mechanism
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Monomethylnitrosamine and methyldiazohydroxide are two proposed N-nitrosamine metabolites, which are formally related by an N → O 1,3-proton shift. Their possible interconversion is an important reaction to investigate in elucidating the pathways involved in the decomposition of carcinogenic N-nitrosamines. Self-consistent field molecular orbital studies using a 4-21G basis set, in which solvation is treated using the supermolcule approach, have led to the proposal of a new low energy pathway for their interconversion; this mechanism involves protonation and the implicit involvement of at least two molecules of water.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00531923
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Theoretical conformational studies on unsaturated aldehydes. II. 4-hydroxy-2-alkenals (1986)
    Springer
    Journal of biological physics 14 (1986), S. 127-132 
    Details
    ISSN: 1573-0689
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Physics
    Notes: Abstract Conformational analyses (using the PCILO method) and structural analyses (using the Hartree-Fock method with the STO-3G and 3-21G basis sets) have been performed on the six 4-hydroxy-s-trans-2-alkenals from 4-hydroxy-2-butenal to 4-hydroxy-2-nonenal. This series of molecules were found to be very similar both structurally and electronically, not only to each other but also to the fives-trans-2-alkenals studied previously.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01857737
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  • 4
    Electronic Resource
    Electronic Resource
    Hydrated carbonium ions as possible nitrosamine metabolites: An ab initio study (1987)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 32 (1987), S. 123-131 
    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: Various isomers of CH3(H2O)n+ (where n = 1-3) have been studied using self-consistent field gradient techniques. The calculations have largely employed a split valence (4-21G) basis set, although the effects of polarization functions and electron correlation have been considered for a model system. A mechanism for the formation of CH3OH from CH3(H2O)n+, involving linear hydration chains, is proposed, and the relevance of the results to the various proposed pathways for the decomposition of nitrosamine metabolites is discussed.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560320111
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  • 5
    Electronic Resource
    Electronic Resource
    Electrostatic potential maps of flavone acetic acids: A new class of antitumor drugs (1988)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 34 (1988), S. 697-705 
    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: Complete geometry optimizations have been carried out with the AM1 method on flavone acetic acid and several of its derivatives. Molecular electrostatic potential maps have been used to predict new com.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560340870
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  • 6
    Electronic Resource
    Electronic Resource
    A theoretical study of N-nitrosamine metabolites: Possible alkylating species in carcinogenesis by N,N'-dimethyl nitrosamine (1986)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 30 (1986), S. 751-762 
    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: The results of ab initio calculations using a 4-21G basis set are reported for various possible metabolites of N,N'-dimethylnitrosamine. The relevance of these results to the nature of the alkylating agent is discussed. Although the calculations widen the range of possible alkylating agents that need to be considered, the diazonium ion appears to be the most likely candidate.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560300604
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  • 7
    Electronic Resource
    Electronic Resource
    Comparison of semiempirical MO methods for open-shell systems (1988)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 9 (1988), S. 702-707 
    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 use of AM1, MNDO, and MNDOC semiempirical MO methods for calculation of heats of formation and ionization potentials of a series of 38 radicals are described. AM1 and MNDO calculations are reported using both half-electron (HE) and Unrestricted Hartree Fock (UHF) wavefunctions. Results show the MNDOC method to give lowest overall errors, being slightly better than the HE-AM1 method. In all cases, the AM1 method shows considerable improvement over MNDO.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcc.540090616
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  • 8
    Electronic Resource
    Electronic Resource
    An investigation of the relative stabilities of the isomers of CF2N2: Comparison of ab initio and MNDO calculations (1987)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 8 (1987), S. 1170-1178 
    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: Ab initio SCF calculations at the HF/3-21G level and semi-empirical MNDO calculations have been used to locate the stationary points on the CF2N2 energy surface. Perfluorodiazomethane is predicted to be most stable isomer, but perfluorodiazirine is predicted to lie only ca 41 kJ higher in energy at the SCF level. There are significant differences between the ab initio and MNDO results for the ordering of some of the isomers. Frequency calculations give results in good agreement with the limited experimental data on these molecules.
    Additional Material: 5 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcc.540080814
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  • 9
    Electronic Resource
    Electronic Resource
    A theoretical study of the rotational isomers of nitrosomethanol by semiempirical (AM1) and ab initio methods (1988)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 9 (1988), S. 212-221 
    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 conformational potential energy surface as a function of the two internal torsion angles in C-nitrosomethanol has been obtained using the semiempirical AM1 method. Optimized geometries are reported for the local minima on this surface and also for the corresponding points on the HF/6-31G, 6-31G*, and 6-31G** surfaces. All methods predict cis and trans minima which occur in degenerate pairs, each pair being connected by a transition state of Cs symmetry. The AM1 structures are found to compare well with the corresponding ab initio structures. Ab initio HF/6-31G and HF/6-31G* harmonic vibrational frequencies are reported for the cis and trans forms of nitrosomethanol. When scaled appropriately the calculated frequencies are found to compare well with experimental frequencies. The ab initio calculations predict the energy barrier for cis → trans isomerization to be between 5.8 and 6.5 kcal/mol with the trans → cis isomerization barrier lying between 2.3 and 6.5 kcal/mol. The corresponding AM1 energy barriers are around 1 kcal/mol lower in energy. The ab initio calculations predict the barrier to conversion between the two cis rotamers to be very small with the AM1 value being around 1 kcal/mol. Both AM1 and ab initio calculations predict interconversion between trans rotamers to require between 1.2 and 1.4 kcal/mol.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcc.540090305
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