Study on the mechanism of furfural to maleic acid oxidized by hydrogen peroxide in formic acid solution

Although the conversion of furfural to formic acid oxidized by H2O2 in formic acid is very high, the molecular mechanism remains unknown. This work describes the entire reaction process of the condensation reaction based on the density functional theory (DFT). It is found that H acts as a shuttle throughout most of the basic reaction steps during this transformation. Besides, Baeyer–Villiger oxidation and Baeyer–Villiger rearrangement are also discovered during this process with the opening of furan ring following afterward. The reactants, products and intermediates in the reaction process are optimized; all possible reaction paths are considered as well as the energy barriers to be overcome at each step. Thermochemical data concerned with the conversion of furfural to maleic acid showed that the maximum energy barrier at 378.15[Formula: see text]K was 39.83[Formula: see text]kcal/mol. The results of this study do not only correspond with the existing conclusions about the reaction in question from previous research but also supplement to the study of the pathways and mechanisms of the reaction, which can provide reference and guidance for further research, both experimentally and theoretically.