Conformational Analysis of Triacylglycerols by Means of Nuclear Magnetic Resonance and Molecular Mechanics

Abstract

The conformational structures around the C-C-C bonds of the glycerol group of three triacylglycerols [C3H (OCOR)3 where the R is CH3, n-C3H7, and n-C17H35, respectively] in CDCl3 solution were investigated by proton nuclear magnetic resonance (1H-NMR) and molecular mechanics calculations (revised QCMP/MM2 force field calculations). The fractional populations of the conformers as determined by both methods showed close agreement. Irrespective of the chain lengths of the acyl group, the three oxygens in the glycerol unit were in the gauche configurations. The most preferred conformation has been shown to be the trans-trans configuration around C-C-C bonds and to constitute about 20% of the possible conformers with lower energy. Both anisochronous methylene protons and the effect of acyl chain length on the glycerol unit have been demonstrated by lanthanide induced shifts in the presence of Eu (fod)3.