Brassidic acid: Preparation from erucic acid and mechanism of elaidinization

Brassidic acid was prepared by elaidinization of 95% erucic acid with 4 mole % nitrous acid at 70 C for 30 min, followed by crystallization from 95% ethanol. Yield was 70%, and purity was 96–97% by gas liquid chromatography and thin layer chromatography. The isomerization reaction was monitored by IRtrans absorption for optimal reaction rate and yield. There was no migration of the double bond. The NMR spectrum of thetrans protons was wide and complex with a chemical shift of 5.34 δ. The nitrous acid elaidinization, generally explained as a free radical process, is believed to be induced initially by the nitrogen dioxide anion (nitrite) and followed immediately by complex formation between the excited triplet anion and the olefin. The complex rotates to the opposite geometric configuration driven by a spin-orbital coupling process. N. Market. Nutr. Res. Div., ARS, USDA.