Decomposition of Peroxides from Methyl Esters of Highly Unsaturated Acids

There are reports on the decomposition of peroxides from fats and esters of common fatty acids, but few papers reported on that of peroxides from esters of highly unsaturated acids. Methyl esters of highly unsaturated acids (saponification value, 172.0; iodine value, 350.9) from cuttlefish oil were oxidized by blowing dried air at 35°C in the scattered sunlight to obtain peroxides with peroxide value (m eq./kg) at 3.00 × 103. This product was decomposed under the conditions of adding no substances, iron soap, or copper soap in the nitrogen atmosphere in the dark, at 35°C. Peroxide value, and ultraviolet and infrared spectra showed that the accelerating effect on the decomposition of peroxides by iron and copper soaps did not appear when the peroxide value was high, but the effect appeared after decompositions considerably performed. As the peroxide value decreased, the amount of conjugated diene decreased, and conjugated triene and higher did not appear in any case. As peroxides decomposed, the-OOH group changed into the-OH group, the α-methylene groups decreased, the formation of aldehydes increased, and the numbers of cis nonconjugated forms did not vary so much. Every effect becomes generally most remarkable, if copper soap is added. The numbers of the double bonds did not increase or decrease prominently.