Double bond location in polyenoic fatty esters through partial oxymercuration

Abstract
A rapid micro‐procedure has been developed to locate double bonds in fatty acid methyl esters containing from one to four double bonds. Reaction of the ester with an equal molar amount of mercuric acetate in methanol and reduction with sodium borohydride, followed by hydrogenation, produce a mixture of monomethoxy alkanoates. The mass spectrum of this mixture is simpler and more definitive than that from the completely methoxylated polyenoate. Only one methoxyl group is present per molecule, and the mass spectrum of the mixture is indicative of all olefinic positions. Four intense ions are observed for all double bonds examined, except Δ3, where the double bond is represented, by only two ions. Hydrogenation in a gas chromatograph reduces total analysis time to 1 hr.