Another possible reason for the improved accuracy observed when only acids or bases are used is the underrepresentation of acid/base pairs where for example, the aromaticity changes upon (de)protonation (e.g., 7a/b). Thus, including both acid and base features was rather leading to redundancy and/or unnecessary features and increasing the size of the model (twice as many bond features). As a solution, some of these redundant features could be removed and the model simplified and focused on the main changing features between acids and bases. A mode to focus on some of the features has been implemented. With this mode, bond order in acids and bases are considered equivalent so bond order of acids is considered only. This focused mode reduces the number of bond features from 14 to 10. Unexpectedly, the accuracy is not improved (MAE = 0.66, entry 22).