Cyclization of linolenic acid by alkali isomerization

Abstract

Summary Methyl linolenate was isomerized by heating in an alkaline ethylene glycol solution for 7 hrs. at 200°. Methyl esters of the isomerized acids were treated with urea in methanol, and the nonurea‐adduct‐forming fraction was distilled. The isomerized esters consisted of 81.8% of nonurea‐adduct‐forming monomeric distillate (NAM), 13.7% nonurea‐adduct‐forming polymeric nondistillable material, and 4.5% of urea adduct‐former The NAM has a maximum absorption in the ultraviolet region at 238 mμ. Ultraviolet absorption extends into the region associated with triene conjugation, but the characteristic structure of triene absorption is absent. Infrared absorption bands in the 10 μ region ordinarily found with trans,trans or cis,trans are absent. The NAM is shown to contain a cyclic monomer by treatment with N‐bromosuc‐cinimide, followed by dehydrobromination with dimethylaniline. The resultant product was oxidized to phthalic acid with permanganate. The NAM was separated both by countercurrent distribution and by gas chromatography into fractions having different ultraviolet absorption spectra. However complete fractionation of the mixture into its pure components has not yet been achieved.