Determine number of fluorines attached to each carbon by ¹³C NMR spectroscopy!

The number of fluorine attached to each carbon is useful in structure analysis of fluorinated compounds. ¹⁹F signals are sometimes observed in a very wide chemical shift range. In that case, It is difficult to uniformly excite all ¹⁹F signals, and hence APT(Attached Proton Test) experiment is more useful than DEPT.
On the other hand, APT is less sensitive than DEPT, so we need to set a higher number of scans. The figures below show ¹⁹F, ¹³C and APT spectra of 5% ethyl 1,1,2,3,3,3-hexafluoropropyl ether in DMSO-d₆ . This sample has ¹⁹F signals spread over a frequency range of over 50 kHz, and so uniform excitation is very challenging.

• In the ¹³C-¹⁹F APT spectra, ¹³C signals of CF₃ and CF have positive signals, while CF₂, C and solvent signals have negative signals.
• By the application of ¹H decoupling, we can increase sensitivity!
• ROYALPROBE HFX can perform these ¹H, ¹⁹F, ¹³C triple-resonance measurements even with a standard 2-channel console!

¹³C {¹H, ¹⁹F} and ¹³C-¹⁹F APT {¹H} spectra, 32 scans

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