Intermolecular Hydrogen Bonding in Alpha-Hydroxy Carboxylic Acids Crystals: Connectivity, Synthons, Supramolecular Motifs

Synthon theory underlies the analysis and empirical prediction of crystal structure. Supramolecular synthons (SMSs) formed by intermolecular hydrogen bonds, such as carboxylic R22(8) C11(4) alcoholic C11(2) ones, are among most popular. The subject this publication is identification specific in alpha-hydroxycarboxylic acids (AHAs) crystals, which carboxyl alcohol fragments present simultaneously. A series 11 single-enantiomeric racemic crystals substituted lactic acids, simplest chiral AHA family, were prepared studied single-crystal X-ray diffraction (SC-XRD) method. Advanced our own published (Cambridge Structural Database) data on 33 structures achiral AHAs diverse revealed that their supramolecular organization differs significantly from simple acids. We found bonds RC(O)O−H···O(H)−C(R′R′′)C(O)OH (in notation HB 12) O=C(OH)C(R′R′′)−O−H···O=C(OH)R′ (HB 23) predominate. frequency interconnected with SMSs. Thus, mentioned above occur but do not dominate crystals. Linear C22(6):12/23 cyclic R22(10):23/23 R33(11):12/23/23 often implemented. An essential role choice played characteristics sample.