The Effect of Fluorine Substituents on Proton Chemical Shifts

FIGURE 2.1. Overview of fluorine chemical shifts (relative to CFC13 (5 = 0)) 

Although the chemical shifts of most commonly encountered organofluorine compounds are upheld of CFC13 and thus have negative values, there are a number of structural situations for fluorine that lead to positive chemical shifts (downfield from CFC13). These include acyl and sulfonyl fluorides as well as the fluorines of SF5 substituents. 

THE EFFECT OF FLUORINE SUBSTITUENTS ON PROTON CHEMICAL SHIFTS 

it is seen that the effect of a single fluorine substituent upon the chemical shifts of protons attached to the same carbon adheres to 

As is consistent with other properties deriving from inductive influences of a substituent, the influence of fluorine substituents on proton chemical shifts drops off dramatically as the fluorine becomes farther removed from the hydrogen in question. Thus, protons on the y-carbon or farther away are essentially unaffected by a single F. 

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