Transesterification

the general name for the processes of alcoholysis (1), acidolysis (2), and ester (RCOOR’) interchange (3):

(1) RCOOR’ + R”OH ⇄ RCOOR” + R’OH

(2) RCOOR’ + R”COOH ⇄ R”COOR’ + RCOOH

(3) RCOOR’ + R”COOR”’ ⇄ RCOOR’” + R”COOR’

The catalysts of transesterification are acids (HCl, HBr, and H₃PO₄), BF₃, and salts of Zn and Co. A shift in the equilibrium toward the right is usually achieved by distillation of the more volatile alcohol (R’OH), acid (RCOOH), or ester.

Transesterification is widely used in preparative organic chemistry and the chemical industry. Thus, bis-β-hydroxyethyl terephthalate, which yields polyethylene terephthalate upon heating to 275°–290°C under vacuum, is obtained from dimethyl terephthalate and ethylene glycol. Transesterification is one of the industrial methods of producing polycarbonates.