Linolenic Acid and Its Isomers

The preparation of linolenic acid by a modification of Rollett's method is described. The melting point of the solid hexabromide is placed at 181.9 °C. The boiling point, specific gravity, iodine value, and refractive index of the ethyl ester, and the melting point of the free acid, were determined. A soft white gummy hexabromide of melting point 145° to 150 °C. was isolated from the ethyl ether soluble hexabromides in proportions approaching that obtained for the solid isomer. Reduction of the so-called liquid hexabromostearic acid gave a product that could not be differentiated from the solid derivative. These facts support the general theory regarding the isomerism noted in the bromo derivatives of the non-conjugated unsaturated fatty acids, and indicate that the so-called a- and β-linolenic acids are identical. No attempt is made to assign any particular cis-trans configuration to this acid, nor to exclude the theoretical existence of seven others.