F NMR chemical shifts in the literature vary strongly, commonly by over 1 ppm, even within the same solvent. Although the reference compound for F NMR spectroscopy, neat CFCl (0 ppm), has been used since the 1950s, clear instructions on how to measure and deploy it in routine measurements were not present until recently. An investigation of the factors influencing the chemical shift in fluorine NMR spectroscopy revealed the solvent to have the largest effect (Δδ = ±2 ppm or more). A solvent-specific reference table with 5 internal reference compounds has been prepared (CFCl, CHF, PhCF, CF and CFCOH) to allow reproducible referencing with an accuracy of Δδ = ±30 ppb. As the chemical shift of CFCl is also affected by the solvent, care must be taken when using dissolved CFCl as reference compound with regards to the chemical shift of neat CFCl (0 ppm). Example of chemical shifts determined against neat CFCl:
For a complete list the reference compounds chemical shifts in 11 deuterated solvents the reader is referred to the cited literature.
A concise list of appropriately referenced chemical shifts of over 240 fluorinated chemicals has also been recently provided.