In a 2017 paper, Leito and co-workers measured the basicity of a range of unsaturated N-heterocycles in several different solvents, including water. We selected 28 of these values for a test set, excluding compounds which were in our initial training set (pyridine and pyridazine). Rowan pKa was able to reproduce the measured pKa values with good accuracy, including effects from stabilizing intramolecular hydrogen bonding which are challenging to identify without explicit consideration of 3D conformers (Figure ). In fact, the largest errors came from overestimating the effect of intramolecular hydrogen bonding: for instance, the basicity of 1,10-phenanthroline was overestimated by about 2.5 pKa units (Figure ), which may point to inaccuracies in the directionality of N-H-N hydrogen bonding in AN2-ωB97MD3. We next examined the ability of Rowan to recapitulate pKa values from the medicinal chemistry literature. In 1972, Miller, Doukas, and Seydel reported that N-aryl sulfonamides served as potent inhibitors of folate synthesis and found that the inhibitory activity could be correlated with the pKa of the sulfonamide N-H. The Rowan pKa workflow recapitulates the experimental trend in pKa values and thus also the observed trend in potency, illustrating the utility of pKa calculations in this system (Figure ).