Synthesis oftrans-3-hexadecenoic acid and oftrans-3-hexadecenoic-1-C14 acid

Abstract
Thetrans-3-hexadecenoic acid has been synthesized. Physical properties and chemical degradation prove its identity with the acid earlier isolated from several plant lipids. In the sequence of the synthesis, the introduction of a terminal triple bond into commercially available 1-tetradecene was performed by bromination and debromination with KOH and NaNH2. Chain elongation by a Grignard reaction with CO2 gave a carboxylic acid with a triple bond in the 2-position. Reduction with LiAlH4 yielded the corresponding alcohol, and reduction of the triple to thetrans double bond was accomplished with Na in ethanol. Bromination of the alcohol with PBr3 and conversion of the bromide to the nitrile with KCN or KC14N elongated the carbon chain to the desired length. Methanolysis with HCl in methanol and saponification with KOH formed the acid with acceptable yields, and in the case of the C14-labeled carboxyl, group, with high specific activity.