Transesterification
Abstract
Transesterification is a reaction in which a new ester is obtained by reacting an alcohol with an ester precursor. The reaction is often performed with a large excess of the incoming alcohol, which can conveniently serve as the solvent. This reaction finds numerous industrial applications, most notably in biodiesel production, in which fatty acid methyl esters are obtained by reacting vegetable oils with methanol, releasing glycerol as a by-product.
Keywords
Ester, Alcohol
Category
Ester, Alcohol
Mechanism
The reaction proceeds in an analogous manner to classic catalyzed esterification. Using a Brønsted acid as catalyst for this example, the carbonyl oxygen atom of the ester is first protonated, thereby activating the carbonyl carbon atom toward nucleophilic attack. The incoming alcohol then performs nucleophilic addition onto this electrophilic site, forming a tetrahedral intermediate, which subsequently loses a proton to give the neutral tetrahedral species. Elimination of the leaving alcohol from this intermediate, followed by deprotonation, yields the new product ester.
Recent review
Norjannah, B.; Ong, H. C.; Masjuki, H. H.; Juan, J. C.; Chong, W. T. Enzymatic transesterification for biodiesel production: a comprehensive review. RSC Adv. 2016, 6, 60034-60055.