The NMR spectra of aromatic fluorocarbons trifluoromethyl- and methoxy-substituted fluorobenzenes

The NMR spectra of some trifluoromethyl- and methoxy-substituted fluorobenzenes have been analysed. The effects of trifluoromethyl substitution on ring fluorine shielding and on F—F coupling constants have been summarised. It has been found that the magnitude of the J (CF 3 —F) ortho coupling constant depends a great deal on the nature of the other substituent ortho to the trifluoromethyl group. The trifluoromethyl group resonance seems to be almost insensitive to methoxy and amino groups.