Synthesis and tribological investigation of lipoyl glycerides

J Agric Food Chem. 2014 Mar 12;62(10):2233-43. doi: 10.1021/jf404289r. Epub 2014 Feb 27.

Abstract

Lipoyl glycerides were synthesized by enzymatic transesterification of lipoic acid with high-oleic sunflower oil in 2-methyl-2-butanol solvent. The synthesis gave a crude product mixture comprising unreacted lipoic acid, free fatty acids, and several lipoyl glyceride structures of varying lipoic acid substitution. A more purified product mixture, devoid of unreacted lipoic acid and free fatty acids, was obtained in 61% yield. The crude and purified product mixtures were thoroughly characterized and their components positively identified. The tribological properties of the product mixtures were further investigated using a variety of methods. The product mixtures displayed significantly improved oxidation stability, cold-flow, and extreme pressure properties over those of the parent high-oleic sunflower oil. The extreme pressure results for the neat products showed a higher weld point for the crude than for the purified mixture. This was attributed to differences in the chemical properties of the components in the two product mixtures.

MeSH terms

  • Calorimetry, Differential Scanning
  • Chemistry Techniques, Synthetic*
  • Glycerides / chemical synthesis
  • Glycerides / chemistry*
  • Lubricants / chemistry*
  • Molecular Structure
  • Oleic Acid / chemistry
  • Oxidation-Reduction
  • Plant Oils / chemistry
  • Pressure
  • Solubility
  • Soybean Oil / chemistry
  • Sunflower Oil
  • Surface Tension
  • Thioctic Acid / chemistry*
  • Viscosity

Substances

  • Glycerides
  • Lubricants
  • Plant Oils
  • Sunflower Oil
  • Oleic Acid
  • Thioctic Acid
  • Soybean Oil