Pertinent 1H Chemical Shift Data

Vicinal coupling constants between fluorine and hydrogen are generally between 18 and 20 Hz for both primary and secondary CF2 groups. 

On the other hand, H-H coupling constants between vicinal hydrogens are much smaller in these compounds, between 4 and 8 Hz. 

TABLE 4.1. Solvent Effects Upon CF2H Proton Chemical Shifts 

There are only small and for most purposes negligible solvent effects upon the CF2H fluorine chemical shifts and the F-H coupling constants. 

Electronegative substituents, such as halogens, alcohol, and ether functions, deshield the fluorine nuclei of CF2 groups when they are attached directly to the carbon bearing two fluorine substituents, whereas electronegative substituents at the -position always have a shielding influence. 

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