Preparation and purity of linoleic acid from commercial corn, cottonseed, and safflower oils

Linoleic acid from commercial corn, cottonseed, and safflower oils was prepared by low temperature crystallization using acetone and petroleum ether as solvents; temperatures ranged between 蜢70 and 50C. This method has the advantages of simple equipment and of flexibility in preparatory capacity. The crystalline fraction obtained at 蜢55C was shown to be 舠pure舡 linoleic acid. Isomerization with potassium tertiary butoxide, oxidative cleavage by periodate‐permanganate, and analysis by liquid‐liquid and gas‐liquid partition chromatography were used to ascertain the purity and the presence of isomers in the final product. This fraction was found to contain 90 to 95%, 9,12 dienoic acid; approximately 5% of dienes with the first double bond at the C 8 position and the second bond either at the C 12 or C 13 positions; and small amounts of nonconjugatable 9,15 cis,cis dienes. Linoleic acid from these oils was similar in composition, except that from corn oil showed the presence of diene with the first double bond at the C 11 position.