Nuclear Spin-Spin Coupling via Nonbonded Interactions. 4. F-F and H-F Coupling in Substituted Benzophenanthrenes.

Article abstract of DOI:10.1021/jo00204a006

NMR measurements of the F-F coupling constants for a series of 4-substituted 1,12-difluorobenzophenanthrenes are reported.The results provide further support for earlier generalizations that intramolecular "through-space" F-F coupling, in contrast to its "through-bond" counterpart, is essentially insensitive to the electronic character of substituents even though they cause significant perturbations in the 19F chemical shifts.The large magnitude "through-space" H-F coupling between H-12 and F-1 for several 4- and 9-substituted 1-fluorobenzophenanthrenes shows a similar insensitivity to substituents.This is consistent with the not ion that "through-space" H-F and F-F coupling have analogous origins in nonbonded overlap interactions.