Tutorial 3.8 Comparing the NMR Spectra of perfluoroanthracene, 1-, 2-, and 9-methoxy- perfluoroanthracene

All four {19}F NMR spectra are shown together in Figure [*]. The parent perfluoroanthracene is at the top, followed by the 1-, 2- and 9-methoxy derivatives. Because the ranges were set to the same on all four spectra, they can be directly compared.

Image F-anthracene-NMR-F
Image F-anthracene-OMe1-NMR-F
Image F-anthracene-OMe2-NMR-F
Image F-anthracene-OMe9-NMR-F
{19}F NMR spectra (from the top): perfluoroanthracene, 1-methoxy-perfluoroanthracene, 2-methoxy-perfluoroanthracene and 9-methoxy-perfluoroanthracene, atom no. 9 selected

In all three derivative spectra, the three main signals observed in the parent are split (due of course to the loss of symmetry) and are shifted downfield. The spectra of the three isomers are sufficiently different that in, e.g., a reaction between perfluoroanthracene and methoxide ion in methanol, provided one isomer was dominant in the reaction mix, it should be possible to determine the actual substitution site - whether at positions 1, 2 or 9 - by comparing the experimentally observed {19}F NMR spectrum with the theoretically simulated spectra.