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

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)(2)C2O4, 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.