Fluorine-19 nuclear magnetic resonance
19F has a nuclear spin of 1/2 and a high magnetogyric ratio, which means that this isotope is highly responsive to NMR measurements. Furthermore, 19F comprises 100% of naturally-occurring fluorine. Other NMR-active nuclei spin 1/2 that are monoisotopic (or nearly so) are 1H and 31P.
Because of its favorable nuclear properties and high abundance, 19F NMR measurements are very fast, comparable with 1H NMR spectroscopy. Indeed the 19F nucleus is the second most receptive NMR nucleus, after the 1H nucleus.
The 19F NMR chemical shift range is very wide, ranging from ca. 550 to -250 ppm, however the most commonly encountered signals arising from organofluorine compounds lie between ca. -50 to -70 ppm (for CF3 groups) to -200 to -220 ppm (for CH2F groups). The very wide spectral range can cause problems in recording spectra, such as poor data resolution and inaccurate integration.
Most commonly 19F NMR spectroscopy is mainly used to analyze the structure of organofluorine compounds. Representative targets of this method are the many pharmaceuticals that contain C-F bonds. The technique is also used to analyze fluoride salts.
- H. Friebolin "Basic One- and Two-Dimensional NMR Spectroscopy", Wiley-VCH, Weinheim, 2011. ISBN 978-3-527-32782-9
- Roy Hoffman (2007). "19Fluorine NMR". Hebrew University.
- Gerken, M.; Boatz, J. A.; Kornath, A.; Haiges, R.; Schneider, S.; Schroer, T.; Christe, K. O. "The 19F NMR shifts are not a measure for the nakedness of the fluoride anion" Journal of Fluorine Chemistry (2002), 116(1), 49-58. doi:10.1016/S0022-1139(02)00101-X
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