Catalysis of Organic..

Sanders et al. 381corresponding alcohol. Thus the hydroformylation product that contains a largenumber of components is converted to a simple mixture of saturated and hydroxyfatty esters. Since the apparent hydrogenation rate of the olefins is faster than thehydrogenation of the aldehydes, there is virtually no unreacted olefin in the finalproduct.PolymerizationThe final step in the formation of the polyol is the reverse of themethanolysis step, however, the alcohol used is not limited to glycerin. Almost anyalcohol can be used as the “initiator” in what might better be termed anoligomerization. Like the methanolysis, this reaction is an equilibrium and can becatalyzed by both acids and bases. The primary difference is that the methanolysisreaction is generally driven by the phase separation of the glycerin, while thepolymerization is driven by removal of methanol (Figure 5).OOH+HOROHMeOOH+ MeOH- MeOHHOROOHOOHOOMeOOOHFigure 5. Transesterification of a hyroxymethylated fatty ester with a polyfunctionalalcoholThe methanolysis catalyst is generally a base such as potassium carbonate, sincethe base catalyzed transesterification is generally lower in energy(5). For thetransesterification of the hydroxymethylated fatty esters, however, a Lewis acid(stannous 2-ethylhexanoate) is employed. Although this catalyst requires highertemperatures to achieve rapid equilibrium, it has the benefit of not requiring removal