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  • 1
    Electronic Resource
    Electronic Resource
    Elektronenstruktur und Spektren von Phenylcycloheptatrienylium-Kationen (1969)
    Springer
    Monatshefte für Chemie 100 (1969), S. 1-27 
    Details
    ISSN: 1434-4475
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Abstract The electron structures of phenylcycloheptatrienylium cations have been studied using one-electron LCAO-MO-methods (HMO- and EHM-method) and strong σ−π-interaction was observed between twisted rings. The calculated results were compared with UV and NMR spectra of 15 cations synthesized in part for the first time. The NMR spectra of phenylcycloheptatrienylium cations with and without substituents in positions 1 and 1′ were found to differ significantly. The differences can be accounted for assuming differently charged hydrogen atoms. A dihedral angle of ω〈45° probably can be assumed for cations without substituents in positions 1 or 1′.
    Notes: Zusammenfassung Die Elektronenstruktur von Phenylcycloheptatrienylium-Kationen wurde mit Hilfe von Einelektronen-LCAO-MO-Methoden (HMO- und EHM-Methode) untersucht. In den verdrehten Strukturen der Kationen tritt starke σ−π-Wechselwirkung von einem Ring zum anderen hin auf. Die Rechenresultate werden mit den UV- und NMR-Spektren von 15 zum Teil neu dargestellten Kationen verglichen. Die NMR-Spektren von Phenylcycloheptatrienyliumionen mit und ohne Substituenten in den Stellungen 1 oder 1′ unterscheiden sich signifikant voneinander. Diese Unterschiede können durch die verschiedenen Ladungsdichten an den einzelnen Wasserstoffatomen erklärt werden. Für die Kationen ohne Substituenten in den Stellungen 1 oder 1′ wird ein dihedraler Winkel ω〈45° wahrscheinlich gemacht.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00938231
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  • 2
    Electronic Resource
    Electronic Resource
    Elektronenlokalisierung im Grundzustand und in angeregten Zuständen Pars-Orbital-Methode, 12. Mitt (1979)
    Springer
    Monatshefte für Chemie 110 (1979), S. 505-515 
    Details
    ISSN: 1434-4475
    Keywords: Character orders ; Electron localization in excited states ; Electron localization in ground states ; Pars orbital method ; Significance index for pattern of fragmentations
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract UsingGleason's theorem the pars orbital concept is developed for excited states of conjugated systems described by CI-methods. A significance index is introduced to evaluate different patterns of fragmentation. The usefulness of this approach is illustrated for butadiene, biphenyl, naphthalene, and azulene.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00938355
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  • 3
    Electronic Resource
    Electronic Resource
    Die Photoenolisierung, Autoxidation und Dimerisation von 2-Isobutyliden-1,3-indandion (1980)
    Springer
    Monatshefte für Chemie 111 (1980), S. 309-329 
    Details
    ISSN: 1434-4475
    Keywords: 2-Alkylidene-1,3-indandiones ; Autoxidation ; 1-Hydroxy-2-vinylinden-3-ones ; Photoenolisation ; 2-Vinyl-1,3-indandion-2-yl radicals
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The title compound,1, slowly decomposes in solution by autodixation, especially in daylight. The chemism of this photoinduced autoxidation has been investigated. Upon irradiation1 passes to the brick red isolable dienol2. The quantum yield is 0.3 at 313 nm in methanol. In solution an equilibrium is set up within several minutes between2 and the colorless deconjugated3. Unpolar or moderately polar solvents shift the equilibrium completely to3, whereas in highly polar solvents2 and3 coexist. In the dark the equilibrium1⇄2 (ca. 50∶1 in methanol) is established very slowly.3 upon irradiation reacts further to dimer8. 2 instantaneously reacts with oxygen. With high oxygen concentrations, hydroperoxide9 is formed, with lower ones dehydrodimer10, inter alia.9 and10 may further form12, 14, and15. These reactions, together with ESR spectroscopy, point to a central role of the free radical13 both in the autoxidation and in the reaction10→14. Basic catalysis sets up an equilibrium between1 and its dimer,17. The photoreaction1→2 has been investigated by sensitizing and quenching experiments.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00938736
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  • 4
    Electronic Resource
    Electronic Resource
    Zur Kenntnis organischerLewis-Säuren, 36.Cis—trans-Gleichgewichte und Konformationen von 2,(x)-Dialkyl-1-dicyanomethylencyclohexanen. Wahlweise einfache Darstellung dercis- odertrans-Formen (1982)
    Springer
    Monatshefte für Chemie 113 (1982), S. 485-494 
    Details
    ISSN: 1434-4475
    Keywords: Conformational energy ; Cyclohexanes, 2,x-dialkyl-1-dicyanomethylene ; Malononitriles, dialkylcyclohexylidene ; 1H-N M R
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Knoevenagel condensation of malononitrile withcis- andtrans-2,5-dimethylcyclohexanone (1 c and1 t, respectively) leads to2 c and2 t, respectively, and withtrans-1-decalone to4 t. The equilibria2 c⇌2 t and4 c⇌4 t have been determined as well as, by means of 270-MHz-1H-NMR, the conformations of these four compounds. The dicyanomethylene group is found to induce axial positions of neighbouring alkyl residues on the cyclohexane ring (or when this is impossible, as in the case of4 t, the twist form of the cyclohexane ring). This results in a strong predominance of thecis isomers in the equilibria2 c⇌2 t and4 c⇌4 t whereas thetrans isomers strongly predominate in the equilibria among the starting ketones. This situation allows the optional preparation of2 c or2 t, and of4 c or4 t, from the more stable starting ketone (or ketone mixture). The free conformational energy of the distorted twist form of4 t amounts to 17 kJ/mol.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00799924
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  • 5
    Electronic Resource
    Electronic Resource
    Topological effect on MO energies, IV. The total π-electron energy ofS- andT-isomers (1984)
    Springer
    Monatshefte für Chemie 115 (1984), S. 1-13 
    Details
    ISSN: 1434-4475
    Keywords: Molecular topology ; TEMO ; Topologically related isomers ; Total π-electron energies
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Es wird allgemein gezeigt, daß bei einemS-T-Isomerenpaar (beschrieben in1, 2) eines alternierenden Kohlenwasserstoffes infolge der HMO π-Elektronen-Gesamtenergie dasS-Isomere stets stabiler sein sollte als dasT-Isomere. Weitere Klassen konjugierter Isomere werden konstruiert und ähnliche Ungleichungen angegeben.
    Notes: Abstract A novel general property of theS- andT-isomers (a concept which has been introduced and elaborated elsewhere1, 2) of alternant hydrocarbons is demonstrated, namely that due to the HMO total π-electron energy theS-isomer should always be more stable than theT-isomer. Some other classes of conjugated isomers are also constructed, for which similar inequalities are derived.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00798416
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  • 6
    Electronic Resource
    Electronic Resource
    Kekulé structure counts: General formulations for primitive coronoid hydrocarbons (1991)
    Springer
    Monatshefte für Chemie 122 (1991), S. 435-444 
    Details
    ISSN: 1434-4475
    Keywords: Kekulé structure ; Coronoid
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Es werden Kekulé-Strukturzählungen (K) für einfache Coronoide behandelt. Die Formel fürK wird durch neugefundene Eigenschaften ergänzt. So wird eine Art von Symmetrie in den mathematischen Formulierungen erreicht. Eine andere generelle Formulierung derK-Zahlen wird in Form von Polynomen bereitgestellt, welche aus uneinsichtigen Gründen als die passenden Polynome von Cyclen identifiziert wurden.
    Notes: Summary The Kekulé structure counts (K) for primitive coronoids are treated. TheK formula which involves the trace of a matrix product is recalled and supplemented with new findings. In this way a kind of symmetry in the mathematical formulations is restored. Another general formulation for theK number is provided in terms of polynomials which, for a somewhat mysterious reason, are identified as the matching polynomials of cycles.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00809795
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  • 7
    Electronic Resource
    Electronic Resource
    NMR-Spektren einiger Benzylidenbarbitursäurederivate (1976)
    Springer
    Monatshefte für Chemie 107 (1976), S. 1115-1125 
    Details
    ISSN: 1434-4475
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The NMR-Spectra of substituted benzylidene barbituric acids, benzylidene dimethylbarbituric acids and some 1,4-and 1,3-cycloaddition products are reported. The signals of the olefinic protons and the N−CH3-signals depend on the conformation of the compounds. The NMR-Spectra of the anions are also given.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00903798
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  • 8
    Electronic Resource
    Electronic Resource
    1,4-Photoaddition of maleic anhydride to chrysene (1981)
    Springer
    Monatshefte für Chemie 112 (1981), S. 659-667 
    Details
    ISSN: 1434-4475
    Keywords: Chrysene ; Maleic anhydride ; Mechanism of photoaddition ; 1,4-Photoaddition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Die Photo-Diels-Alder-Reaktion von Maleinsäureanhydrid mit Chrysen ergibt Chryseno[4,5-efg]-isobenzofuran-4,6-dion (VI). Schweratomexperimente mit Xenon als äußerer Störer zeigen, daß die Reaktion vom niedrigst angeregten Singulettzustand des Chrysens ausgeht. Die Abstraktion von Wasserstoffatomen aus dem primärenDiels-Alder-Addukt IV durch das Lösungsmittel CH2Cl2 folgt möglicherweise einem Zweistufenmechanismus. Die Reaktion stellt einen neuen Typ von Photoreaktion dar; möglicherweise folgt sie einem Mechanismus, der in der Photochemie neuartig ist.
    Notes: Abstract The photoDiels-Alder reaction of maleic anhydride with chrysene yields chryseno[4,5-efg]isobenzofuran-4,6-dion (VI). Heavy atom experiments using xenon as an external perturber show that the reaction occurs via the lowest singlet excited state of chrysene. Hydrogen is abstracted from the primaryDiels-Alder adduct IV by the solvent CH2Cl2 possibly in a two-step mechanism. The reaction presents a new type of photoreaction, its mechanism possibly follows a scheme not considered so far in photochemistry.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00899679
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  • 9
    Electronic Resource
    Electronic Resource
    Note on the topological information content of simple graphs (1985)
    Springer
    Monatshefte für Chemie 116 (1985), S. 211-216 
    Details
    ISSN: 1434-4475
    Keywords: Automorphism groups ; Graph theory ; Information theory ; Topological information content
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Wie gezeigt wird, besitzen schlichte Graphen gleichen topologischen Informationsgehalt, wenn ihre Automorphisgruppen isomorph sind. Ferner: sind die Automorphismengruppen zweier Graphen durch Kranzprodukte darstellbar deren Feingruppen isomorph sind, dann haben diese beiden Graphen gleichen topologischen Informationsgehalt. Drei Graphen, welche mit organischen Molekülen korrespondieren, illustrieren das Ergebnis.
    Notes: Abstract It is shown that simple graphs gave equal topological information content if their automorphism groups are isomorphic. Further, if the automorphism groups of two graphs are represented by wreath products of which the inner groups are isomorphic, then the two graphs possess equal topological information content. Three graphs which correspond to organic molecules illustrate this finding.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00798456
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  • 10
    Electronic Resource
    Electronic Resource
    HMO-elektronen-Struktur von Annulenen mit Bindungsalternanz (1981)
    Springer
    Theoretical chemistry accounts 59 (1981), S. 1-8 
    Details
    ISSN: 1432-2234
    Keywords: HMO ; Annulene ; Bond alternation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Abstract Analytical expressions for the LCAO-coefficients and the elements of the charge-bond order-matrix are derived for 4n and for (4n +2) annulenes with alternant bond lengths. Due to the reorganization of the orbital scheme there is a discontinuity in the bond orders of 4n -annulenes at the symmetry change fromD (2n)h toD (4n)h .
    Notes: Zusammenfassung Für 4n- und (4n + 2)-Annulene mit Bindungsalternanz werden analytische Ausdrücke für die LCAO-Koeffizienten und die Elemente der Ladungs-/ Bindungsordnungsmatrix hergeleitet. Die auf die Umordnung des Orbital-schemas zurückgehende sprunghafte Änderung der Bindungsordnungen in 4n-Annulenen beim SymmetrieübergangD (2n)h →D (4n)h wird diskutiert.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00574431
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