13C splittings of proton and fluorine resonance spectra

Abstract

13C satellites in proton and fluorine N.M.R. spectra have been used to obtain the coupling constants J 13c-h and J 13c-f for a number of ortho-, meta- and para-substituted fluorobenzenes. These coupling constants are found to depend on the substituent as well as the position of substitution. The 13C-H coupling constants, for a particular position, in general, increase with increase of the electron withdrawing power (expressed through Hammett σ-parameters) of the substituents. For a particular substituent, the values of 13C-H coupling constants increase with decrease of σ values and are found to change with the position of the substitution in the order meta < ortho < para. Such regularities are not found for 13C-F coupling constants.