Indirect Electro-Synthesization Of Benzoic Acid And Its Derivatives

This paper investigates electrochemical preparation benzoic acid and its derivatives. Organic electrsynthesis adopt electron as reagent, will not import any impurity in reaction system. Electrosynthesis also have advantages ,such as mild condition, little side reactions, little pollution and high rate of production. In a word, organic electrosynthesis has been an important part of green chemistry. It has been applied in many organic syntheses.Indirect electro-synthesis is a means that make produce by a medium that can transfer electrons, at the same time, medium change its valence state. After this, medium regenerates by electrolyte. Medium that regenerates react with reagents again and so on. Compared with direct electro-synthesis,indirect electro-synthesis has many merits:Fist,medium reduce reactional activation energy and restrain side reations, so it can improve reactional selectivity and the yield and current efficiency. Medium can be used again. So it can reduce prime cost and pollution.Electro-chemical oxidation of Cr³⁺ on the Pb/PbO₂ electrode has been studied. The optimum conditions of electro-oxidation of Cr³⁺ are included current density 198 A·m^-2, the concentration of Cr³⁺: 0.35 mol·L^-1, the concentration of sulfuric acid: 4 mol·L^-1,the temperature: 44℃ , the concentration of ammonium sulfate: 0.15 mol·L^-1 .Under these conditions, the conversion rate of Cr³⁺ and the current efficiency are 74.28 % and 94.57 %, respectively.The optimum conditions of toluene indirect electro-oxidation to benzoic acid has been obtained through a series of experiments of the concentration of sulphate acid,the reactional temperature,the reagent ratio of Cr⁶⁺ to toluene.The optimum conditions are that the reagent ratio of Cr⁶⁺ to toluene is 2.5:1, the reactional temperature is 90℃, the concentration of sulfuric acid is 3.5 mol·L^-1, the concentration of Cr⁶⁺ is 0.4 mol·L^-1.In...