A simple calculational model for predicting the site for nucleophilic substitution in aromatic perfluorocarbons

We present a simple model for predicting the principal site for nucleophilic substitution in aromatic perfluorocarbons. Our model is based on the relative stabilities of the Meisenheimer complexes as calculated using density functional theory with a modest basis set. (Hartree-Fock theory will do just as well.) Although such calculations were essentially impossible to carry out when early theoretical work on this topic was undertaken in the mid-1960s and early 1970s, they are now routine and full geometry optimization for any of the systems studied in this work can be completed in a matter of minutes with modern quantum chemistry programs and computational hardware. Predictions from our model agree with experimental observations for 16 aromatic perfluorocarbons, and together with additional NMR calculations, lead us to conclude that the earlier prediction that perfluoroanthracene undergoes nucleophilic substitution in the 2-position is incorrect, and is based on a misinterpretation of the experimental 19F NMR spectrum.