19F n.m.r spectra of polyfluoroquinolines. Long range inter‐ring 19F19F coupling constants and 19F chemical shifts

Abstract

AbstractThe signs and magnitudes of every fluorine–fluorine coupling constant in perfluoroquinoline (1), 2,4‐dichloropentafluoroquinoline (2) and 2‐bromohexafluoroquinoline (3) have been determined by 19F n.m.r. These provide an unambiguous assignment of the spectrum of the first compound and its derivatives. Inter‐ring fluorine–fluorine coupling constants were found to be positive over an odd number of bonds and negative over an even number of bonds, similar to that observed in proton–proton coupling constants in multicyclic systems.The 19F chemical shifts of perfluoroquinoline and its protonated salt are reported and directly correlated with SCF MO calculated π‐electron densities at both fluorine and bonded carbon atoms.