## 3 Results
### Evaluation of the J-Couplings Derived from the JCS  
With a Larmor frequency difference of \(\approx\)130 Hz, the strong heteronuclear \(J\)-coupling condition was satisfied for \(J_{\rm HF}>5.1\) Hz, which was present in each molecule of our sample set (Table 2). Therefore, complex splitting patterns from the heteronuclear and homonuclear \(J\)-couplings were expected [14]. Figure 4: The \({}^{19}\)F region of the JCS for hexafluorobenzene (**a**), monofluuorobenzene (**b**), 1,2-difluorobenzene, 1,3-difluorobenzene (**c**), 1,4-difluorobenzene (**d**), 1,2,4-trifluorobenzene (**e**), 1,2,4,5-tetrafluorobenzene (**g**), and pentafluorobenzene (**h**). The black lines are the experimentally measured spectra, the red lines are the simulated spectra, and the blue lines are the residuals between the experimental and simulated spectra. Each spectrum also has a scaling factor, denoted below the compound name, that indicates the amount the experimental, simulated, and residual data was multiplied such that the maximum peak intensities of spectra (**a**–**h**) were equivalent. The \(J\)-couplings obtained from the JCS simulations corresponded to the previously measured high field \(J\)-couplings, and were within 0.58 Hz for all \(J\)-couplings and all samples (Figure 5), with the majority of the couplings within \(\pm\) 0.25 Hz [44; 45]. The largest discrepancy (in Hz) occurred in pentafluorobenzene, in which the \({}^{3}\)\({}_{\rm FF}\) and \({}^{4}\)\({}_{\rm FF}\) differed by 0.53 and 0.58 Hz, respectively. However, with the other \(J\)-coupling deviations in the literature values for pentafluorobenzene, the \(R\)-factor increased by 9.86%, indicating a worse fit of the experimental JCS. More recent \(J\)-couplings have been measured in the literature for pentafluorobenzene and have also been reported in Table 2 and Figure 5 [44]. However, these \(J\)-couplings varied even more drastically (0.68-1.16 Hz) for several \({}^{3}\)\({}_{\rm FF}\) couplings and resulted in increasing the \(R\)-factor to 45.32%. The differences in the \(J\)-couplings from the literature may be attributed to differences in choice of solvent and/or concentration, which can affect inter- and intra-molecular interactions and cause perturbations in the observed \(J\)-couplings [52]. For example, comparisons of the \(J\)-couplings between a 95% pentafluorobenzene solution in CCl\({}_{3}\)F solution and a 10% solution in CDCl\({}_{3}\) solution showed differences of \(\approx\)1.18-1.31 Hz, which are well within the differences reported above [44; 53]. The concentration effects on the \(J\)-coupling and corresponding JCS have also been previously demonstrated for \({}^{13}\)C-labeled methanol, where a 0.9 Hz difference was observed between the neat solvent and a 0.6 M solution in deuterium oxide (D\({}_{2}\)O) [43]. Since all samples in the current study were analyzed as neat solvents, subtle differences between the \(J\)-couplings are not unexpected when compared to typical 75% solutions reported in the literature [45]. Thus, \(J\)-coupled spectroscopy in the strong heteronuclear \(J\)-coupling regime may inform inter- and intra-molecular interactions governing changes in \(J\)-coupling. In addition to the magnitude of the \(J\)-coupling, each \(J\)-coupling has an associated sign. The relative sign relationships between different \(J\)-couplings, obtained from the JCS, are in agreement with previous studies [44; 45]. Absolute signs for the JCS were chosen such that they agree with previous studies, since only the relative signs of the \(J\)-couplings can be determined from a one-pulse experiment at low field (_vide infra_). However, recent work suggests that the determination of absolute sign may be accomplished using more sophisticated pulse sequences that have been applied to high field spectra and may be amenable to LF NMR techniques [54; 55; 56]. The absolute signs may also be determined  
Figure 5: Differences in the \(J\)-couplings between the JCS and the literature values reported in [44] and [45].