We knew going into the SAMPL6 challenge that complex polyprotic molecules would fall outside the domain of applicability for our model, however, other functional groups appear to also be poorly represented. For example, molecule SM20 has only one ionizable group, the acidic imide group (Figure ). While our training set includes some similar functional groups, there was not a wide diversity. Specifically, none in the training set had a sulfur one bond away. This is also evident in our prediction 7.31±1.84 where the large uncertainty reflects the lack of similarity between this ionizable group and our training set. Expanding our training data to include polyprotic molecules was already in our plans, but considering more complex mono-or diprotic Fig. SM06 provided feedback on our ability to accurate identify ionizable groups as our method only finds two (blue), notably missing the acid amide (red) Fig. Our prediction for SM20 was still rather inaccurate, despite it being monoprotic (blue). This is likely due to a lack of representation of imide groups in similar environments in our training set.