Our studies use an experimental dataset curated by Ertl 12b based on the 200 most common aryl substituents in the ChEMBL database, of which 89 have experimentally determined Hammett parameters available (Figure ). Molecules (in which each substituent is appended to a phenyl group) were first converted from SMILES format to 3D structures with added hydrogens using RDKit. Conformer ensembles for each structure were then generated with CREST, from which all structures were fully optimized with DFT. We used the B3LYP functional with a Becke-Johnson damped Grimme D3dispersion correction and def2-TZVP basis set in chloroform using SMD implicit solvation for geometry optimizations. All structures were verified as minima by analysis of vibrational frequencies. The DFT-computed charges and NMR shielding tensors were obtained at the same level of theory. Single-point analyses with other density functionals (M06-2X, wB97XD) and solvent models yield parameters that are highly correlated with those discussed in the manuscript; the statistical comparisons made in the main text are independent of the level of theory used (see Supporting Information, section S2 for detailed comparison). For the DFT optimized structures, Class II, III, and IV atomic charges along with NMR isotropic shielding tensors (proportional to computed NMR chemical shifts) were obtained at the same level of theory, all of which are widely available in modern electronic structure packages. Variations of these charge models were also computed, including Minimal-Basis