In this study, we aimed to identify portions of small molecule chemical space which are particularly informative for force field development. After filtering eMolecules as described in Section 3.3, we were left with 2.7 million molecules. We optimized each of these molecules with each of the five force fields considered -GAFF, GAFF2, MMFF94, MMFF94S, and SMIRNOFF99Frosst . For any given molecule, we performed pairwise comparisons of these five minimized conformers, yielding ten comparisons that we here call "molecule pairs" (though each member of a molecule pair is actually the same molecule in different conformations). Each of the molecule pairs was evaluated for geometric differences using Torsion Fingerprint Deviation (TFD) and TanimotoCombo . We limited our analysis to molecules having 25 or fewer heavy atoms. Furthermore, we restricted our analysis to molecule pairs which yielded a TFD value less than 0.60 and a TanimotoCombo value between 0.25 and 2.0. These cutoffs were chosen based on visual inspection, as explained in detail in Section 3. Last, we sort molecules into different sets, which were then characterized using the Checkmol functional group identification tool.