Fluorooleic acid
Fluorooleic acid is a naturally occurring, unsaturated, and fluorinated fatty acid. The Delta notation is 18-F-18:1-delta-9c.
Natural occurrence
Fluoroleic acid, along with some other ω-fluoro-substituted fatty acids, occurs at about 10–20% in the seed oil of Dichapetalum toxicarium, a plant native to Sierra Leone in West Africa.Biosynthesis
Unlike many other plants, Dichapetalum toxicarium can accumulate much more fluoride, even when the soil content is not particularly high. In young leaves, this is converted into monofluoroacetate, which is stored in the leaves around the flowers. During seed formation, the fluoroacetate is transferred there and converted into long-chain fluorinated fatty acids, including fluorooleic acid.Synthesis
One method starts with 8-fluorooctanol, which is first reacted with phosphorus tribromide. The product of this reaction is then reacted with sodium acetylide in xylene/DMF. Then, the reaction takes place with 1-chloro-7-iodoheptane and metallic lithium in liquid ammonia and finally with sodium cyanide in DMSO, yielding the nitrile of fluorooleic acid. This reacts with hydrogen peroxide and potassium hydroxide in acetone to form the amide, and then with potassium hydroxide in ethanol to form the carboxylic acid. The triple bond can be converted into a -double bond by Lindlar catalyst.Fluoroleic acid can also be isolated from Dichapetalum toxicarium. A chromatography method optimized for the separation of fluorinated fatty acids has been published.