Electrooxidation of 2-Methylpyridine in Acetone/Water Mixed Solvents

In an electrolytic cell with proton exchange membrane as diaphragm,2-pyridinecarboxylic acid was prepared in acetone/water mixed solvents by direct electrooxidation of 2-methylpyridine at a PbO_2 electrode.The effect of volume ratio of acetone to water,temperature,anode potential,concentration of sulfuric acid and 2-methylpyridine on the selectivity and the current efficiency were studied by using cyclic voltammetry,linear scan voltammetry and potentiostatic electrolysis.The optimal reaction conditions were found as volume ratio of acetone to water 3∶1,reaction temperature 30 ℃,anode potential 1.75～1.80 V,concentration of sulfuric acid 1.0～1.2 mol/L and concentration of 2-methylpyridine 0.5 mol/L.The selectivity and current efficiency for electrosynthesis of 2-pyridinecarboxylic acid in acetone/water mixed solvents reached 88.7% and 48.3%,respectively;whereas with pure water as solvent under same conditions,the selectivity and current efficiency were 67.4% and 42.2%,respectively.