Transesterification of Diethyl Carbonate with Methanol Catalyzed by Sodium Methoxide

The mechanism of sodium methoxide-catalyzed transesterification of diethyl carbonate with metha-nol to dimethyl carbonate has been studied by DFT quantum chemical calculations using B3LYP functional. Ethoxy groups in the substrate are replaced successively through four-coordinate carbon intermediates which undergo decomposition. Sodium methoxide with carbonates forms pre-reaction complexes where the sodium cation is coordinated to the carbonate fragment. These complexes are characterized by enhanced electron-donating power of the methoxy fragment and increased electron-withdrawing power of the carbonate fragment, which favors the transesterification process.