Location of double bonds in long chain esters by methoxymercuration-demercuration followed by mass spectroscopy

Methyl esters of simple mono-, di-, and triunsaturated long chain fatty acids quantitatively react with mercuric acetate in methanol to produce methoxyacetoxymercuri derivatives. Demercuration of these derivatives with sodium borohydride yields methoxylated fatty acid esters, readily isolable by thin layer chromatography. Mass spectra of the methoxylated esters are characterized by intense peaks due to cleavage adjacent to methoxy-functions which allow the position of the original double bond in the chain to be ascertained. The methoxylated derivatives are conveniently analyzed by gas liquid chrovmatography and also by combined gas chromatographymass spectrometry. In comparison with other methods for double bond location, the procedure described in simple, reliable, and rapid.