CHIRAL BETA-HYDROXYCARBONYL COMPOUNDS BASED ON (-)-MENTHONE - STRUCTURE AND BEHAVIOR IN LIQUID-CRYSTALLINE SYSTEMS

It has been established by X-ray structural analysis that '-biphenyl-4 -yl-1'-hydroxy)methyl-p-menthan-3-one, one of the products of the reac tion of (-)-menthone triisopropyloxytitanium enolate with 4-phenylbenz aldehyde, has a 1R,2S,4S,1'S configuration. In crystals, this beta-hyd roxyketone adopts a chair conformation with equatorial methyl and isop ropyl groups and an axial 2-(1'-biphenyl-4-yl-1'-hydroxy)methyl substi tuent. Unlike the stereoisomeric compound with the 1R,2R,4S,1'S config uration, the exocyclic fragment of which has an intramolecular >C=O... H-O- hydrogen bond in crystals and solutions, in the crystals of the 1 R,2S,4S,1'S ketol under study, molecules are linked by a network of co operative -O-H...O-H...O-H... hydrogen bonds. Based on the results of molecular mechanics calculations and experimental data of H-1 NMR and IR spectroscopy, conformations of molecules of this compound, which ar e in equilibrium in solution, have been characterized. Based on data o n spatial structures of stereoisomeric beta-hydroxyketones and the cha racter of H-bonds formed by these compounds, the characteristic featur es of the effect of these chiral alloying additives on the supramolecu lar structure and macroscopic properties of liquid crystalline systems have been interpreted.