The NMR spectra of some fluorinated pyridine derivatives

The ¹H and ¹⁹F spectra of a variety of mono- and di- fluorinated pyridines are examined, and compared with the corresponding spectra of the pyridinium ions. The magnitudes and signs of the ¹H? ¹⁹F coupling constants are in general in accord with those observed for the corresponding ¹H? ¹H couplings, with an exaggerated range. Large changes in the NMR parameters are observed on protonation of the nitrogen, ³J(H? F) changing sign in some of the α-fluoropyridine derivatives.