Synthesis and Tribological Investigation of Lipoyl Glycerides

• Published in: Journal of agricultural and food chemistry Vol. 62; no. 10; pp. 2233 - 2243
• Main Authors: Biresaw, Girma, Laszlo, Joseph A, Evans, Kervin O, Compton, David L, Bantchev, Grigor B
• Format: Journal Article
• Language: English
• Published: WASHINGTON American Chemical Society 12.03.2014; Amer Chemical Soc
• Subjects: Agriculture; Agriculture, Multidisciplinary; alcohols; Calorimetry, Differential Scanning; Chemistry; Chemistry Techniques, Synthetic; Chemistry, Applied; cold; density; differential scanning calorimetry; enzymatic interesterification; food chemistry; Food Science & Technology; free fatty acids; Glycerides - chemical synthesis; Glycerides - chemistry; high performance liquid chromatography; Life Sciences & Biomedicine; lipoic acid; Lubricants - chemistry; mass spectrometry; mixing; Molecular Structure; Oleic Acid - chemistry; oxidation; Oxidation-Reduction; Physical Sciences; Plant Oils - chemistry; Pressure; Science & Technology; Solubility; solvents; Soybean Oil - chemistry; Sunflower Oil; Surface Tension; Thioctic Acid - chemistry; transesterification; triacylglycerols; Viscosity; oxidation stability; high-oleic sunflower oil; viscosity; 4-ball antiwear; soybean oil; enzymatic transesterification; 4-ball extreme pressure; cold-flow properties; lipoic acid; viscosity index; biolubricant; ACID; STABILITY; CHEMICAL-STRUCTURE; VEGETABLE-OILS
• ISSN: 0021-8561; 1520-5118
• DOI: 10.1021/jf404289r

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.