When determining the F chemical shifts of aromatic fluorine atoms, specifically phenyl fluorides, there is another equation that allows for an approximation. Adopted from "Structure Determination of Organic Compounds," this equation is:where Z is the SSCS value for a substituent in a given position relative to the fluorine atom. Some representative values for use in this equation are provided in the table below:
The data shown above are only representative of some trends and molecules. Other sources and data tables can be consulted for a more comprehensive list of trends in F chemical shifts. Something to note is that, historically, most literature sources switched the convention of using negatives. Therefore, be wary of the sign of values reported in other sources.