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

Thermotropic cholesteric liquid crystals made of mixtures of cholester ic esters and of a DELTA(chi) < 0 nematic (ZLI 2806) may be used as NM R solvents to visualize enantiomers. Proton decoupled deuterium NM R s pectra of a racemic mixture show that the quality of the spectra stron gly 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 b est 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.