Using NMR spectroscopy for the measurement of compounds containing fluorine
Fluorine is an important element in industrial chemistry and has applications in a wide range of industries, such as pharmaceuticals, agrochemicals, polymers, surfactants and solvents. It is estimated that more than 20% of all pharmaceutical compounds contain fluorine. This includes some of the commercially important drugs such as Prozac (fluoxetine) and Paxil (paroxetine).
Nuclear Magnetic Resonance (NMR) spectroscopy is a valuable technique for the measurement of compounds containing fluorine especially organofluorine compounds. After 1H and 13C NMR, 19F is the most common nucleus studied by this technique. 19F nuclei are spin ½ nuclei and a have a high gyromagnetic ratio, which means that they have a high receptivity for NMR measurements. The 19F isotope has 100% natural abundance, giving high NMR sensitivity. The 19F resonance frequency on X-Pulse, a 1.45T magnet, is 56.76 MHz which is sufficiently close to the resonance frequency of 1H such that 1H and 19F spectra can be measured using the same probe.
A series of spectra have been collected to demonstrate the 19F and 1H capability and performance of the instrument using the same probe.
Trifluorotoluene is a useful reference material for 19F NMR spectroscopy and can be used in a similar way to tetramethylsilane (TMS) for 1H measurements.
A mixture of two fluorine containing chemicals; Trifluorotoluene and trifluoroethanol.
The compound 5-Bromo-1,2,3-trifluorobenzene.
A comparison has been made of the 19F spectra of two different positional isomers of bromotrifluorobenzene.
X-Pulse s a high performance benchtop NMR spectrometer that does not require external services, such as liquid cryogens or compressed air, and can be placed in the laboratory rather than in a specialised NMR facility. Spectra can be collected within a couple of minutes using standard 5mm NMR tubes.