VISUALIZATION OF ENANTIOMERS THROUGH DEUTERIUM NMR IN CHOLESTERICS OPTIMIZATION OF THE CHIRAL LIQUID-CRYSTAL SOLVENT

Thermotropic cholesteric liquid crystals made of mixtures of cholesteric esters and of a DELTA(chi) < 0 nematic (ZLI 2806) may be used as NMR solvents to visualize enantiomers. Proton decoupled deuterium NM R spectra of a racemic mixture show that the quality of the spectra strongly depends on the temperature and on the nature and the concentration of the ester. A relationship between the spectral resolution and the presence of textural defects in the mesophase is also discussed. The best results, both for spectral resolution and enantiomeric separation. were obtained with a 45/55 by weight mixture of cholesteryl butyrate and ZLI 2806 at 368 K.