Abstract
Methyl linoleate, methyl linolenate and safflower oil were respectively isomerized rapidly to the conjugated esters with addition of potassium tert-butoxide, and dimethyl sulf oxide or dimethyl f ormamide at zoom temperature. The loss of ester group in the conversion was little. The conjugated diene/conjugated triene ratio in the isomerized linolenate was approximately 3 : 1. The isomerization of linoleate gave the cis, trans conjugated dienoate chiefly. The isomerization of cis, traps- and trans, trans-9, 12-octadecadienoate gave the mixture containing 4153% cis, trans- and 47 '59% traps, traces conjugated dienoate. This suggests the proceeding of the cis, trans isomerization toward equilibrium composition in the conjugation process. At the tert butoxide concentration of 0.050.3 mol, the rate of isomerization of trans, trans dienoate is expressed in the following form :
rate = K (tert-butoxide) 2.5 (polyenoic acid ester).
However, at higher concentration the rate becomes independent of base concentration. In the isomerization in the sealed tube at 70°C, methyl linoleate mostly changed to the tert-butyl ester of the conjugated acids, and methyl linolenate to the polymerized products, which did not show maximum absorption at 265270mμ.
