Submitted to: Journal of the American Oil Chemists' Society
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 13, 2008
Publication Date: May 6, 2008
Citation: Dailey Jr, O.D., Prevost, N.T., Strahan, Gary D. 2008. Synthesis of branched-chain derivatives of methyl oleate. Journal of the American Oil Chemists' Society. 85:647-653. Interpretive Summary: The use of vegetable oils as alternative diesel fuels (biodiesel) has been investigated for over a century. Biodiesel is presently typically obtained by the conversion of vegetable oils or animal fat to simple esters of fatty acids. These products, usually methyl or ethyl esters, can be utilized as alternative fuels or extenders in diesel engines. However, the relatively poor low-temperature properties (freezing in cold climates) of these biodiesel fuels present a problem in their development and commercialization. Oleic acid and linoleic acid are the most abundant fatty acids of many vegetable oils, including cottonseed oil. As part of a project to develop new value-added industrial applications for cottonseed oil (such as biodiesel, fuel additives, and lubricants), studies were conducted in the synthetic conversion of oleic acid to branched-chain fatty acids. Esters of branched-chain fatty acids should have improved or superior low-temperature properties. In these studies, methyl oleate (a major component of biodiesel) was converted in a series of reactions to several different branched-chain derivatives. The synthesized products exhibited significantly lower re-crystallization temperatures in comparison with methyl oleate. This research benefits farmers of cotton and other oilseed crops, oil chemists, and the automotive industry in that it demonstrates that biodiesel (using methyl oleate as a model compound) can be converted to branched-chain derivatives exhibiting enhanced low-temperature properties.
Technical Abstract: Oleic acid and linoleic acid are the most abundant fatty acids of cottonseed oil. As part of a project to develop new value-added industrial applications for cottonseed oil (such as biodiesel, fuel additives, and lubricants), studies were conducted in the synthetic conversion of oleic acid to branched-chain fatty acids. The conversion of vegetable oils to esters of branched-chain alcohols has been reported to improve low-temperature properties, demonstrated by reduced crystallization onset temperatures. Simple monoalkyl esters containing branched-chain fatty acids could have improved or superior low-temperature properties. In these studies, methyl oleate was brominated in the allylic position and subsequently treated with organocuprate reagents to produce novel branched-chain derivatives (methyl, n-butyl, phenyl). Modification of reaction conditions (lower temperature, less organocuprate reagent) afforded predominantly the desired n-butyl and phenyl derivatives and minimized products resulting from attack on the ester functionality. Details of the syntheses, characterization, and the properties of the products (with emphasis on low-temperature properties) are discussed.