LINOLEIC ACID AND ITS ISOMERS

Abstract

Linoleic acid has been prepared from sunflower seed oil by a modification of Rollett's method. The melting point of the solid tetrabromostearic acid is placed at 115.2 °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. Linoleamide was prepared, and its melting point is placed at approximately 58 °C. Through rebromination of the prepared linoleic acid, the isomeric liquid tetrabromostearic acid was isolated, and is described. Its reduced acid is shown to be identical with that derived from the solid isomer. From these data and additional data from the literature, it was concluded that bromination and debromination cause no cis-trans isomerization, and that the two pairs of optically active enantiomorphous bromo derivatives exist, not because of their derivation from different acids, but rather because of the four asymmetric carbon atoms which they contain. Therefore, only one naturally occurring linoleic acid is at present known which is identical with that produced through reduction of the tetrabromide that melts at 115.2 °C. or the corresponding liquid derivative. No attempt is made to assign any particular cis-trans configuration to this acid, or to exclude the theoretical existence of three others.