Efficient synthesis of diethyl oxalate from transesterification of dimethyl oxalate and ethanol using alkaline catalysts and kinetic studies of transesterification

Abstract

A series of catalysts such as soluble alkalis (e.g. C₄H₉ONa, C₂H₅ONa, CH₃ONa, NaOH, Na₂CO₃, NaHCO₃, and Na₂C₂O₄) and amines (e.g. DBU, DABCO, C₆H₁₅N, (NH₄)₂C₂O₄, NH₄C₂H₃O₂, and C₁₆H₃₆BrN) with different base strengths were studied for the transesterification of dimethyl oxalate (DMO) and ethanol (EtOH). It is of great interest that sodium tert-butoxide exhibited a TOF value of 274 032 h⁻¹ at room temperature during the transesterification process. The pK_b value was introduced and the relationship between the base strength and catalytic efficiency was established. A lower pK_b value resulted in a stronger nucleophilicity and a higher catalytic efficiency. In addition, the reaction kinetics and mechanism were well studied, and the transesterification results of multiple raw materials with different molecular structures were in accordance with the deduced mechanism.