The Unsaturated Fatty Acids of Milk Fat III. Geometrical Isomerism

The monoethenoid fatty acids of animal fats are largely, but not exclusively, of cis configuration. Bertram (2) first reported the isolation of vaccenic acid from beef tallow, sheep fat, and milk fat and concluded that it was a /k ~, ~-~octadecenoic acid of trans configuration. Other investigators (3, 6) have confirmed the presence of vaccenic acid in milk fat, and Rao and Daubert (13) have presented additional evidence confirming the trans configuration of this acid. Swern etal. ( Although Hilditch and Longenecker (8) reported that milk fat contained C~, C~, C,._,, and C~o monoethenoid fatty acids with double bonds in the /k 9, ~-position, the geometrical configuration of these acids has not been determined.