Synthesis Of Benzaldehyde And 4-Bromo-2-fluorobenzaldehyde By Oxidation With Mn₂O₃

Fluorinated benzaldehyde is a kind of key intermediates in chemical and pharmaceutical field. At present, it is prepared via hydrolysis or electrolysis,causing serious pollution with low yeild.In this paper, a new manufacturing process has been proposed by oxidation with Mn2O3 to produce benzaldehyde and 4-bromo-2-fluorobenzaldehyde.In synthesis of benzaldehyde, the effect of each factor, such as temperature,amount of Mn2O3, concentration of sulfuric acid, amount of sulfuric acid has been studied by orthogonal experiment. The optimum process condition has been found: reacting at 65℃with 1.4160g Mn2O3 and 30ml sulfuric acid with concentration of 7.3mol/L. Under this condition, the yield was 93.27%.In synthesis of 4-bromo-2-fluorobenzaldehyde, affecting factors: temperature, amount of Mn2O3, concentration of sulfuric acid, amount of sulfuric acid have been studied by orthogonal experiment. The optimum process condition have been found: reacting at 75℃with 0.56g Mn2O3 and 35ml sulfuric acid with concentration of 7.6mol/L. Under the optimum condition, the yield of 4-bromo-2-fluorobenzaldehyde was 59.89%.Researches on kinetics of toluene and 4-bromo-2-fluorotoluene also have been conducted, which show that the overall reactions of both reagents are typical of zero order serial reaction and with activation energy about 69kJ/mol and 237kJ/mol repectively.In addition, the water phase treated with active carbon and adjusted PH with surfuric acid can be resued,making the synthetic route a environment friendly process.