CONFORMATION ANALYSIS OF GLYCERIDES BY NUCLEAR-MAGNETIC-RESONANCE

The conformation of the glycerol moiety of five glycerides, tri-, 1,3- di-, 1,2-di-, 1-mono-, 2-monopalmitin, was studied by using proton nuc lear magnetic resonance (H-1-NMR) method. The spectra of 2-monopalmiti n in chloroform-d(1) and in tetrahydrofuran-d(8) solutions showed the existence of the conformer, in which the O-C-alpha-C-beta-C-gamma, O-C -alpha-C-beta-O, O-C-beta-C-gamma-O and C-alpha-C-beta-C-gamma-O angle have gauche configuration. The increase in the polarity of the soluti on decreased the population of this gauche conformer. The activation e nergy for the rotational barriers for the C-alpha-C-beta and C-beta-C- gamma were large enough to separate the spectra of this conformer from other conformers by H-1-NMR. This gauche conformation of 2-monopalmit in may possibly be stabilized by the intramolecular hydrogen bonds in low polarity solutions. In the case of the other glycerides, this conf ormer was not observed. The fractional populations of the conformers o f each glyceride were also analyzed by comparing the coupling constant s of the proton in the glycerol moiety in several solutions.