Solvent Dependence of H-F Coupling Parameters in Fluorobenzene

Solvent dependence of NMR spectral parameters has been the object of considerable interest in recent years (see Ref. 1 for a brief summary). More recently attention has been devoted to the solvent dependence of NMR parameters in fluorine-containing compounds. In their investigation of fluorobenzene, Mohanty and Venkateswarlu observed the effect of solvents on the proton and fluorine chemical shifts, but did not report any dependence of the H-K or H-F couplings on the solvent medium.² For 1,2-dichlorofluoroethylene Bell and Danyluk found a linear correlation between the directly bonded ¹³C-H and ¹³C-F couplings and the H-F couplings.³ These results, along with linear correlations between the ¹³C-H (or ¹³C-F) coupling and the proton (or fluorine) chemical shift, led to the inference that the medium effect acts to change the coupling parameters and shieldings by a similar mechanism.