AbstractAn analysis of the19F n.m.r. spectra of heptafluoroisoquinoline and hexafluoro‐1‐methoxyisoquinoline is presented. As in heptafluoroquinoline, the inter‐ring FF coupling constants alternate in sign and magnitude and are positive over an odd number of bonds. They correlate with SCFMO carbon–carbon polarizabilities and this infers that the long‐range coupling mechanism is dominated by the contribution from the π‐e