Nuclear magnetic resonance study of molecules in anisotropic systems. Part 9. Solution structure and preferred orientation of myo-inositol in a lyotropic liquid crystal

Abstract

¹ H.N.m.r. spectra of myo-inositol have been measured in a lyotropic liquid crystal containing potassium laurate. Variable-temperature experiments revealed an increased participation of direct couplings in the spectra on lowering the temperature of a sample from an isotropic phase. Analysis of the ordered spectra obtained at 28 and 22 °C afforded values for the direct couplings between protons. The distance ratio r_2,6/r_3,5 was determined to be 0.92 from the relevant direct couplings. The direct coupling data have been interpreted in terms of a reasonable model of molecular structure; however, a full analysis of the direct couplings to give precise structural and order parameters was unsuccessful because of a relatively low degree of order in the mesophase. The principal axis system for the order tensor differs as much as 34° from that for the moment of inertia; it is therefore suggested that a type of solute–solvent interaction dominates the orientation of myo-inositol. The ¹H n.m.r. spectrum of myo-inositol in D₂O has also been analysed, to derive the indirect couplings used in the analysis of the ordered spectra.