One interaction (edge) between hydroxyl groups corresponds to a hydrogen bond (H-bond) between them. The presence of an edge between two phenyl groups can indicate either a pure π π interaction between the aromatic rings or C H π interactions between a C H bond in one molecule and the π-electron cloud of an aromatic ring. Finally, OH-π bonded isomers correspond either to an H-bond between an aromatic hydrogen atom and the hydroxyl group or a hydroxyl proton with the π-electron cloud.