Enantiomeric Analysis of Homologous Series of Secondary Alcohols by Deuterium NMR Spectroscopy in a Chiral Nematic Liquid Crystal: Influence of Molecular Geometry on Chiral Discrimination
NMR measurements of the differential ordering effect (DOE) are presented for homologous series of 22 chiral secondary aliphatic alcohols dissolved in a poly-(gamma-benzyl-L-glutamate) (PBLG)/dichloromethane liquid-crystalline solvent. The quadrupolar splittings of the solutes, which were deuterated at their chiral centres, were measured as a function of the PBLG concentration and temperature. The proton dipolar splittings of the dichloromethane in each sample were also measured and used as a reference. The results are analysed qualitatively in terms of the structures of the molecules and their asymmetric (or chiral) characteristics. Emphasis is put on comparative analysis of the chiral discrimination in members of each particular homologous series and on evaluating the Limits of the technique for molecules that have two very similar groups attached to their stereogenic centres.