## 1 Introduction  
In earlier work we introduced a simple calculational model for predicting the primary substitution site for nucleophilic substitution involving the replacement of fluorine, initially in aromatic perfluorocarbons [1] and subsequently in fluorinated aromatic systems containing both ring heteroatoms (principally nitrogen, but also oxygen, phosphorus and sulphur) and non-fluorine substituents [2]. The model assumes the standard two-stage description of nucleophilic aromatic substitution involving the formation of a negatively charged intermediate, known as a Meisenheimer complex [3], which is the anionic equivalent of the Wheland intermediate in electrophilic substitution [4]. The negative charge in the Meisenheimer complex is delocalized into the aromatic \(\pi\)-system, which like the Wheland intermediate, can be considered as a resonance hybrid of multiple canonical forms. Specifically, the model involves calculating the energy of all possible Meisenheimer complexes at a standard level of _ab initio_ theory (basic Hartree-Fock theory with the 6-31G* basis set [5]: HF/6-31G*), using the fluoride ion as a \"typical\" nucleophile, with the preferred site for nucleophilic substitution corresponding to the most stable (lowest energy) complex. This simple model has been remarkably successful in predicting not only the primary site in aromatic nucleophilic substitution reactions, but also secondary sites. In our two previous papers on this topic [1,2] we have presented correct predictions for primary and secondary substitution sites for over 70 different nucleophilic substitution reactions. Currently we are aware of only one system (perfluorophthalazine) where our model fails to predict the correct primary substitution site (although there are certainly likely to be more). Although the model is only meant to be qualitative we note a recent attempt to use a very similar model quantitatively [6]. Our Meisenheimer model nominally involves a purely thermodynamic rationale, _i.e._, the thermodynamically most stable Meisenheimer complex is the one most likely to form, and the substitution pattern follows directly from that. The underlying assumptions are, first, that the substitution reaction is indeed two-step, involving an at least meta-stable Meisenheimer complex as intermediate; second, that barrier heights--both from reactant to intermediate and intermediate to product--are either more or less identical in all cases, and can therefore be ignored, or reflect the thermodynamic stability in the Meisenheimer complex so that considering only the latter gives the correct substitution pattern; and third, that varying the reaction conditions, principally the solvent and the actual nucleophile itself, makes no difference to the preferred substitution site, _i.e._, the mechanism is essentially the same for all nucleophiles in all solvents. Even for nucleophilic substitution reactions that are one-step, _i.e._, do not involve a Meisenheimer intermediate, the model can still be successfully applied provided the Meisenheimer complex can reliably predict the relative energies in the respective transition states. In the last few years liquid ammonia has become a very useful reagent for aminating aromatic fluorocarbons. It has proven to be a useful synthetic method as it is capable of substituting the amino group (-NH\({}_{2}\)) for fluorine site-specifically in high yield. This use of liquid ammonia has been pioneered primarily by the [PERSON] group at Novosibirsk State University in Russia. They have published a number of papers from 2007 onwards involving amination of polyfluorinated benzenes and pyridines [7,8], perfluorobiphenyl [7], perfluoronaphthalene [9] and tetrafluorophthalic acid [10]. Additionally, [PERSON] and coworkers have found that liquid ammonia animates 1-nitro-2,4-difluorobenzene dominantly in the 2-position [11]. Collectively these papers present around 20 different nucleophilic substitution reactions (all aminations), the vast majority of which we have not looked at in our previous work.