Exploiting Supramolecular Synthons in Cocrystals of Two Racetams with 4-Hydroxybenzoic Acid and 4-Hydroxybenzamide Coformers

Structures of three cocrystals nootropic racetams were studied. They included two phenylpiracetam (PPA) with 4-hydroxybenzoic acid (HBA) different stoichiometries, PPA·HBA and PPA·2HBA, cocrystal 2-(4-phenyl-2-oxopyrrolidin-1-yl)-N’-isopropylideneacetohydrazide (PPAH) 4-hydroxybenzamide (HBD), PPAH·HBD·(acetone solvate). X-ray study the pure forms PPA PPAH was also carried out to identify variations molecular synthons under influence conformers. The structures revealed diversity supramolecular namely, amide-amide, amide-acid, acid-acid, hydroxyl-hydroxyl; however, very similar chains found in dimers PPAH·HBD. In addition, conformational observed as disorder PPA·2HBA it earlier for rac-PPA that allows consideration an example partial solid solution. Quantum chemical calculations conformers demonstrated most conformers, energy differences do not exceed 2 kcal/mol suggests packing conditions (in this case R- S-enantiomers intend occupy same position crystal) on conformation.