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Sorry that I've been out of touch so long. It's been an insanely busy semester so far. I'm trying to find out what the standard reference compound used in F19 NMR is. For proton NMR the reference is TMS, but I can't find any literature describing what the reference compound is for F19 NMR. Any thoughts?

Hope that you are well,

Hi Mike, good to hear from you! I'm not surprised that you've been so busy! I have not done any ¹⁹F-NMR myself, but here is some information about fluorine NMR references from Fluorine NMR, by J. T. Gerig (http://www.biophysics.org/education/gerig.pdf):

"Fluorine chemical shifts span a very wide range and there is no single fluorine-containing compound that is experimentally convenient for use as a universal reference compound. A fluorine reference is chosen on a more ad hoc basis and is usually a compound that is chemically similar to the one under examination. Since fluorine shielding parameters are significantly more sensitive to sample conditions than proton shielding parameters it is important when describing fluorine NMR experiments to specify the reference compound, its concentration, and the temperature of the sample.
Table 2 gives the approximate fluorine chemical shifts for fluorine-containing part-structures typically found in fluorine NMR studies of biological systems. The shifts are given relative to fluorotrichloromethane (CFCl3), a reference compound with a small fluorine shielding parameter, trifluoroacetic acid (CF3COOH), an often convenient, water-soluble compound, and fluorobenzene. These data are provided only as an aid in designing experiments; the exact shifts for any fluorine-containing group depend strongly on the structural details of the system under study. For example, aromatic fluorine shifts appear over a range of over 70 ppm since they are sensitive to the nature of the substituents on the fluoroaromatic ring and depend on solvent and solute concentrations."

It looks like CFCl3, TFA, and PhF are the most common references. Web Elements gives CFCl3 as the "common reference compound" for fluorine NMR, and a note on another message board states, "Another useful ¹⁹F shift reference is "Annual Reports on NMR Spectroscopy - Volume 14" edited by G.A. Webb, Academic Press 1983. All chemical shift in this book are reported in ppm with CFCl3 as the reference." So, you might want to go with CFCl3 if it can be used in aquous solutions. Good Luck!

Thanks for your help! The compound I want to run the NMR on dissolves in chloroform, so CFCl3 may be a good choice.

Thanks again! Your help is very appreciated! :-)

OK Mike, good luck with your project! Is this a triflate compound like you were working with before? I remember it was giving you some headaches!

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