Erucic acid is a monounsaturated omega-9 fatty acid with 22 carbon atoms and one cis double bond at position 13. It occurs naturally in high concentrations in seeds of Brassicaceae plants such as rapeseed, mustard, and wallflower. Historically, high-erucic-acid rapeseed oil was used industrially but limited in food due to potential cardiotoxicity observed in animal studies. Modern low-erucic varieties (canola) contain <2% erucic acid. It is employed in lubricants, plastics, and as a precursor for behenic acid. Chemically stable under normal conditions, it participates in typical carboxylic acid reactions including esterification and hydrogenation.