An important step in evaluating E min as a synthesizability descriptor is establishing whether a molecule or not is synthesizable. We label QM9 molecules as synthesizable if they are reported in either the PubChem 32 or eMolecules database, 33 and assume unreported molecules are unsynthesizable. We acknowledge two limitations of classifying molecules classified as unsynthesizable this way: 1) not all historically synthesized molecules are reported in these databases, and 2) unreported molecules are not necessarily unsynthesizable. However, because QM9 includes fairly-small molecules, we hypothesize its chemical and structural space is likely to be well studied for synthesis. Molecules that are not attempted for synthesis likely require expensive precursors and, as such, are of low interest in future discovery. Nevertheless, we continue our work knowing that our models may produce more false negatives than expected due to the assumption that unreported molecules are highly likely to be unsynthesizable.