Ab initio insight into furan conversion to levulinate ester in reaction with methylal and methanol

Abstract

Recently, methyl levulinate (MLA) has attracted remarkable attention as a promising fuel additive and its synthesis route from furan and dimethoxymethane (DMM or methylal) has been exploited, but the reaction pathway remains indistinct. In this work, we study the conversion of furan into MLA in reaction with DMM and methanol using ab initio calculations with double-ζ polarization basis sets plus supercell method and B3LYP/6-311+G* basis sets plus cluster method. Our calculations reveal that the reaction of furan + DMM to 2-methoxymethyl-furan (MMF) + methanol is endothermic in vacuum but exothermic in methanol solvent, while the reaction of MMF + water to MLA is exothermic both in vacuum and methanol solvent environments. Moreover, we identify the reaction sites of the individual reactant molecules by analyzing their Fukui functions and verify the Brønsted acid–base reaction fashions for these reactions. Finally, we determine the activation energies for the reactions without and with a protonated methanol molecule, together with the detailed geometries of the intermediates.