Liquid crystals as solvents

Dewar, M. and Schroeder, J.P, Liquid-crystals as solvents. II. Further studies of liquid crystals as stationary phases in gas-liquid chromatography, J. Org. Chem., 30, 3485, 1965. 

For molecules dissolved in a nematic thermotropic liquid-crystal, the direct coupling constants can be determined and from these the molecular geometry can be calculated. If the satellites are determined, not only the proton structure but the carbon skeleton of the molecule can be established. Oxirane has been measured in two laboratories. It proved possible to determine the orientation, the sign of the indirect coupling constant, and the geometry. Enantiomers can readily be determined by recording measurements in optically active liquid-crystals as solvents. ... 

An overview of the apphcation of NMR to the field of liquid crystals over the past 50 years has been presented and the important aspects of proton and deuterium NMR have been delineated. The use of liquid crystals as solvents in NMR spectroscopy has been reviewed." Reviews on NMR studies of orientational order with 20 references, rotational diffusion of liquid crystals in the nematic phase and NMR spectroscopy in liquid crystals and membranes are available. A review on the application of spectroscopic methods to liquid crystalline phases has appeared during the period under report and it includes a discussion of the NMR methods. NMR and other methods used to determine the order parameters of nematics have been reviewed. ... 

In particular, we were interested in the possibility of obtaining asymmetric induction by using cholesteric liquid crystals as solvents. 

Liquid Crystals as Solvents for Spectroscopic, Chemical Reaction, and Gas Chromatographic Applications... 

The special combination of orientational order and mobility possessed by liquid crystals, the wide variation in these properties in different liquid crystalline types, and the fact that bulk orientation can be easily controlled by a number of different methods have led to numerous applications in which liquid crystals are employed as anisotropic solvents for the study of various physicochemical properties of molecules. This chapter deals with the use of liquid crystals as solvents or supports in spectroscopic applications, in gas chromatography, and for chemical reaction. In each case, the emphasis is on studies in which the solute is of primary interest, and in which calamitic liquid crystals are employed as solvents to control orientation or mobility. Spectroscopic studies in which some property of the mesophase is of primary interest, whether they involve a study of probe molecules or the liquid crystal itself, are treated in earlier chapters and will not be dealt with here. In many cases, studies of this type are intimately re-... 

The number of studies of the use of thermotropic liquid crystals as solvents to alter... 

Tables 3 and 4 (see pages 874 and 878) provide a bibliography of the wide variety of reactions that has been investigated using cal-amitic liquid crystals as solvents since publication of the first edition of The Handbook. In most studies, the reactions of interest were also investigated in model isotropic solvents for comparison. A number of the entries relate to reactions that exhibit little or no solvent control on the reactivity. In many cases, the lack of an effect may be attributed to the solvent s inability to impart its anisotropy to the substrate(s) or due to phase separation. In any case, these failures are just as...

---