transzészterifikációval

Transesterification, or transzészterifikáció in Hungarian, is a chemical reaction in which the alkoxy group of an ester is exchanged with the alkoxy group of another alcohol. The general reaction can be written as R1-COOR2 + R3-OH ⇌ R1-COOR3 + R2OH. The reaction is catalyzed by acids, bases, or enzymes. Base-catalyzed transesterification uses alkoxide bases such as methoxide or hydroxide and proceeds rapidly at moderate temperatures when excess alcohol is used to drive the equilibrium toward the desired ester. Acid-catalyzed variants are slower but can tolerate more water and free fatty acids; they are used for esters that do not readily undergo base-catalysis. Enzymatic transesterification uses immobilized lipases and can operate under milder conditions, often with fewer byproducts.

Applications include production of biodiesel: triglycerides from fats or oils react with methanol (or ethanol) to yield fatty acid methyl esters (FAME) and glycerol. The process requires removal of glycerol and minimizing soap formation from free fatty acids. In polymer chemistry, transesterification is used to rearrange polyesters and to exchange ester groups during resin modification or recycling.

Key considerations are reaction conditions, catalyst choice, alcohol-to-ester ratio, water content, and purity of reactants. Advantages of transesterification include versatility and the ability to tailor ester products; limitations include catalyst sensitivity to impurities and equilibrium constraints.