Intramolecular screening effects on nuclear magnetic resonance chemical shifts. Part III. Some investigations of the correlation between fluorine-19 nuclear screening and intramolecular electric fields, and an assignment of the 19F resonance spectrum of perfluorobicyclo[2,2,1]heptane

Authors:
  • JHJ. Homer
    J. Homer
  • DCD. Callaghan
    D. Callaghan
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Abstract
Perfluorobicyclo[2,2,1]heptane, trans-perfluorodecalin, and perfluorocyclohexane are taken as the basis for the investigation of methods for the correlation of fluorine-19 nuclear screening with intramolecular electric fields. The most satisfactory correlation is obtained by use of an equation of the form Δσ=–XΔEz– YΔ(E2)– ZΔ〈E2〉. The point of origin of the electric fields associated with C–F bonds is investigated, together with the validity of including contributions from C–C bonds to the 〈E2〉 term.