METATHESIS OF UNSATURATED FATTY ACIDS: SYNTHESIS OF LONG CHAIN UNSATURATED ALPHA, OMEGA-DICARBOXYLIC ACIDS

Authors: Ngo, Helen; Jones, Kerby; Foglia, Thomas

Submitted to: Journal of the American Oil Chemists' Society
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/15/2006
Publication Date: 7/1/2006
Citation: Ngo, H., Jones, K.C., Foglia, T.A. 2006. Metathesis of unsaturated fatty acids: synthesis of long chain unsaturated alpha, omega-dicarboxylic acids. Journal of the American Oil Chemists' Society. 83(7)629-634.

Interpretive Summary: Simple unsaturated fatty acids such as oleic acid, which are common to most fats and oils, are often converted into diacids that are widely used in the production of polyester and polyamide polymers. Present chemical methods of producing these diacids, however, require the use of hazardous reagents and are either energy intensive or environmentally unfriendly. Fermentative routes to this important class of materials, while considered green processes, are costly in comparison to chemical methods of production and are limited in the types of diacids that can be made. In this paper, we describe a catalytic approach to the direct production of diacids from commonly found fatty acids in high yields and conversions. The process requires no solvents or reagents other than the catalyst used in the process and the diacids are easily isolated by simple recrystallization processes.

Technical Abstract: The self-metathesis of readily available monounsaturated fatty acids has the potential of being an important pathway for the synthesis of symmetrical long-chain unsaturated-alpha, omega-dicarboxylic acids (C18-C26). Previous studies on the self-metathesis of monounsaturated fatty acid esters using ruthenium catalysts in solution, however, suffered from low conversions as a result of the thermodynamic control of the reaction. We have found that the second generation Grubbs catalyst can effectively catalyze the solvent-free self-metathesis of monounsaturated fatty acids of varying purity (from 90% to 99%) to afford two important products--monounsaturated dicarboxylic acids and hydrocarbons--in very high molar conversions (> 80%). This solvent-free self-metathesis reaction also works for monounsaturated fatty acids containing additional functional groups. Reactions were conducted at catalyst loadings as low as 0.005 mol% and turnover numbers as high as 10,800 could be obtained. This discovery represents an attractive approach to the large-scale production of useful monounsaturated-alpha,omega-dicarboxylic acids and long-chain unsaturated hydrocarbons by means of this solvent-free ruthenium-catalyzed self-metathesis of readily available monounsaturated fatty acids.