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  • Physical Chemistry  (2)
  • Computational Chemistry and Molecular Modeling  (1)
  • 1
    Digitale Medien
    Digitale Medien
    A theoretical and experimental investigation of acid catalyzed rearrangements of small [n]cyclophanes (1989)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 2 (1989), S. 331-348 
    Details
    ISSN: 0894-3230
    Schlagwort(e): Organic Chemistry ; Physical Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: The difference in reactivity of small [n]cyclophanes towards CF3CO2H is discussed in terms of charge densities, strain energies and proton affinities. These data are calculated with MNDO and MINDO/3 for para-, meta- and ortho-cyclophanes and for their ipso-protonation products; an attempt is made to transform gas phase ΔHf0 values into liquid phase ΔH0f values. Experimental evidence is presented that the acid catalyzed rearrangement of [5]paracyclophane to its ortho-isomer proceeds via two consecutive 1,2-carbon shifts without deprotonation; intermediate adducts were identified by NMR-spectroscopy. Thus, a gradual shift in reaction pattern in the series [4]-, [5]- and [6]paracyclophane is observed experimentally, in line with the calculational results.
    Zusätzliches Material: 2 Tab.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/poc.610020405
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  • 2
    Digitale Medien
    Digitale Medien
    [4]Paracyclophane: MNDO and STO-3G molecular structure and strain energyTaken in part from Ref. 1. (1990)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 3 (1990), S. 295-300 
    Details
    ISSN: 0894-3230
    Schlagwort(e): Organic Chemistry ; Physical Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: The molecular structure of [4]paracyclophane was optimized at the semiempirical MNDO and the ab initio STO-3G level. A comparison of the results showed that the benzene ring is much less bent at the STO-3G level. Although some bond alternation is predicted at both levels of theory, the aromatic carbon-carbon bond lengths are still in the range typical of highly delocalized compounds. The calculated strain energy [SE(tot.)] of [4]paracyclophane is larger for the STO-3G structure. Nevertheless, the distributions of SE(tot.) over the bent benzene ring [SE(bb.)] and the oligomethylene bridge [SE(br.)] are the same for the MNDO and STO-3G structures.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/poc.610030505
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  • 3
    Digitale Medien
    Digitale Medien
    MNDO Calculations on [n]metacyclophanes (1987)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 8 (1987), S. 1154-1169 
    Details
    ISSN: 0192-8651
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Biochemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Informatik
    Notizen: MNDO calculations on [n]metacyclophanes and a variety of related compounds are reported. An analysis of the strain, imposed by the oligomethylene bridge, and its distribution over the distorted benzene ring and the oligomethylene bridge is presented. The effect of strain and bending of the benzene ring on aromatic delocalization is investigated by a comparison of ΔHof of the bent benzene systems with that of a correspondingly bent, but localized 1,3,5-cyclohexatriene. The results indicate that, even in the case of the highly bent [4]metacyclophane (1a), localization is unfavorable by about 10 kcal/mol.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/jcc.540080813
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