Soy fatty acid oxidation with sodium hypochlorite monitored by nuclear magnetic resonance spectroscopy

Abstract

AbstractThe oxidation process of soy fatty acids by sodium hypochlorite with ruthenium trichloride catalyst was examined at different temperatures and active chlorine:fatty acid molar ratios. 1H and 13C distortionless enhancement by polarized transfer nuclear magnetic resonance (NMR) spectroscopy techniques were used to monitor oxidation of the double bonds in unsaturated lipids by measuring the peak integration ratio of double‐bond peaks:methylene‐methyl peaks. This NMR monitoring technique proved to be an excellent means to quantify double‐bond reactions. Gas chromatography‐mass spectrometry was used to identify mono‐ and diacid products, separated by hexane/methylene chloride extraction, as well as other oxidation products. While the presence of ruthenium catalyst increased the initial rate of oxidation, it also catalyzed the decomposition of hypochlorite, decreasing the available reactive chlorine, resulting in a delay in complete oxidation. A 9:1 molar ratio of active chlorine to fatty acids completely oxidized all double bonds of soy fatty acids. However, the yield of low‐molecular‐weight monoacid oxidation products was only 17%, indicating the probable formation of hydroxy fatty acids.