NMR active nuclei and isotopes as tracers of Group 17 elements

Although F, Cl, Br and I all possess spin active nuclei, in practice only 19F (100%, I = 1/2) is used routinely. Fluorine-19 NMR spectroscopy is a valuable tool in the elucidation of structures and reaction mechanisms of F-containing compounds.

    Artificial isotopes of F include ¹⁸F (β⁺e mitter, t_1/2= 1.83 h)and ²⁰F (β^- emitter, t_1/2= 11.0 s). The former is the longest lived radioisotope of F and may be used as a radioactive tracer. The ²⁰F isotope has application in F dating of bones and teeth; these usually contain apatite  which is slowly converted to fluorapatite when the mineral is buried in the soil. By using the technique of neutron activation analysis, naturally occurring ¹⁹F is converted to ²⁰F by neutron bombardment; the radioactive decay of the latter is then monitored, allowing the amount of ¹⁹F originally present in the sample to be determined.