Interbenzylic ¹⁹F,¹⁹F spin‐spin coupling constants in bis(fluoromethyl) arenes

Abstract

Five-to eleven-bond F,F spin coupling is observed in bis(fluoromethy1)arenes. According to INDOMO calculations, these couplings are transmitted mainly via the aromatic --system. The low preference of 1,4-(CH&z-benzene for the conformation in which the C-F bonds are perpendicular to the aromatic ring is shown by the strong increase of '4FF) upon double ortho-substitution.Some time ago' we demonstrated the existence of large interbenzylic 31P,31P spin-spin coupling constants, over up to nine bonds, in aromatic compounds carrying two CH,P(O)(OR), groups. We now report five-to eleven-bond 19F,19F couplings in a number of bis(fluoromethy1)arenes (see Table 1).