Fluorine magnetic resonance studies. VII. Fluorine-fluorine coupling over five bonds in 1-Fluoro-2-(2'-fluorophenyl)ethanes

Abstract

Spin-spin coupling between an aromatic fluorine and fluorines in an adjacent side chain (Ar-C-C-F), with J values in the range 2-5 Hz, is reported for four new compounds. The coupling probably arises from through-space interactions taking place when rotation of the side chain brings the two types of fluorine into close proximity. In a Diels-Alder adduct of fluoranil and 1-fluoro-4-methyl- anthracene, this proximity is denied the fluorines and no coupling is observed.