Electrochemical Chlorination of Levulinic Acid

Abstract

Levulinic acid is a cellulose-derived, sustainable feedstock with significant potential for use in renewable, carbon-based polymer and chemical synthesis. In this work, electrochemical chlorination has been investigated as a method for preparing chlorinated levulinic acid derivatives, which can serve as valuable intermediates for the synthesis of other compounds and polymers. Electrochemical chlorination was studied using carbon or platinum cathodes, carbon anodes in undivided and divided cells, under a variety of conditions including electrolysis of levulinic acid in HCl, NaCl with acidic, basic and neutral conditions. The experiment using a divided cell with platinum cathode, graphite anode, ceramic porous cup membrane and using levulinic acid in 11 M HCl in anode, 11 M HCl in cathode compartments, and 0.10 A cm⁻¹ current density produced the highest levulinic acid conversion of 94% producing a mixture of 3-chloro-, 5-chloro-, 3,3-dichloro 3,5-dichloro- and 5,5-dichloro-levulinic acid in 58:19:9:8:6 mole ratio in 70% coulombic efficiency. The more rapid formation of 3-chloro relative to 5-chloro-levulinic acid suggests that electrophilic chlorination proceeds via an ionic mechanism involving enol or enolate intermediates. Monitoring the reaction over six hours showed gradual dichlorination of the initially formed monochlorinated products.