Dechlorination of chloroaromatics by electrocatalytic reduction over palladium-loaded carbon felt at room temperature

The selective dechlorination of various chloroaromatics in water-MeOH medium containing trifluoroacetic acid and tetraalkylammonium salts was successfully performed over Pd-loaded carbon felt cathode at room temperature. The reactivities of 2,4-dichlorophenyl derivatives varied in the order: 2,4 dichlorotoluene < 2,4-dichlorophenol ≤ 2,4-dichloroanisole ≤ 2,4-dichlorobenzoic acid < 2,4-dichlorophenoxyacetic acid < 2,4-dichlorophenethyl alcohol. For 2,4-dihaloanisoles, the ease of reductive cleavage of C---X (X=halogen) bond was as follows: F Cl < Br. For monochlorobiphenyls, the dechlorination and product recovery efficiencies were remarkably affected by tetraalkylammonium cations of different size. The reaction scheme for the selective electrocatalytic dehalogenation of haloaromatics over Pd-loaded felt cathode was proposed.