Metathesis of Unsaturated Fatty Esters

The development of a homogeneous catalyst (WCl6Sn(CH3)4) for the metathesis of unsaturated fatty esters encloses new routes in fat chemistry. By these reactions an exchange of alkylidene moities takes place, thus methyl oleate is converted into 9‐octadecene and 9‐octadecenedioic dimethyl ester. The metathesis of poly‐unsaturated esters leads to a much larger number of products, namely polyenes, mono‐ and dicarboxylic esters, and cyclopolyenes. Specially the formation of 1,4‐cyclohexadiene is of great interest. The metathesis of unsaturated fatty oils and the cometathesis with alkenes are also possible. Reactants of technical purity with a low acid value (< 0.1) can undergo metathesis. The reaction is essentially thermoneutral; the distribution of products is statistical and no completion of the reaction occurs in one way or an other. Thus separation of reaction products and unconverted material is necessary. By the metathesis of mono‐unsaturated esters this can be done by fractional crystallization. A review is given of these and other applications on account of the latest research development.