Fig. 1

Structures of the solute molecules capable of forming the intramolecular hydrogen bonds. Functional groups involved in the hydrogen bonds are indicated in red. 1–3, 4–6, 7–13, and 14–21 belong to training set for SAMPL4, test set of SAMPL4, training set of FSD, and test set of FSD molecules, respectively. 2-Hydroxybenzaldehyde (5 and 15) and 1-amino-4-hydroxyanthraquinone (6 and 18) are shown in duplicate because they belong to different data sets and their hydration free energies were calculated with different atomic parameters