title: Synthesis and tribological investigation of lipoyl glycerides.
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.
authors.affiliation: Bio-Oils Research Unit and ‡Renewable Product Technology Research Unit, National Center for Agricultural Utilization Research, Agricultural Research Service, U.S. Department of Agriculture, 1815 North University Street, Peoria, Illinois 61604, United States.
authors.forename: Girma
authors.initials: G
authors.lastname: Biresaw
authors.forename: Joseph A
authors.initials: JA
authors.lastname: Laszlo
authors.forename: Kervin O
authors.initials: KO
authors.lastname: Evans
authors.forename: David L
authors.initials: DL
authors.lastname: Compton
authors.forename: Grigor B
authors.initials: GB
authors.lastname: Bantchev
mesh_terms: D002152:Calorimetry, Differential Scanning; D060326:Chemistry Techniques, Synthetic; D005989:Glycerides / Q000138:chemical synthesis / Q000737:chemistry*; D054327:Lubricants / Q000737:chemistry*; D015394:Molecular Structure; D019301:Oleic Acid / Q000737:chemistry; D010084:Oxidation-Reduction; D010938:Plant Oils / Q000737:chemistry; D011312:Pressure; D012995:Solubility; D013024:Soybean Oil / Q000737:chemistry; D000074242:Sunflower Oil; D013500:Surface Tension; D008063:Thioctic Acid / Q000737:chemistry*; D014783:Viscosity
chemical_list: D005989:Glycerides; D054327:Lubricants; D010938:Plant Oils; D000074242:Sunflower Oil; D019301:Oleic Acid; D008063:Thioctic Acid; D013024:Soybean Oil