Study On Selective Oxidation And Preparation Of 4-nitro-o-xylene

2-Methyl-4-nitrobenzoic acid was prepared by selective nitration and selective oxidation, using o-xylene as starting material.The nitration selectivity of o-xylene using nitric acid in the presence of various catalysts was studied.The experimental results showed that the ratio of 4-nitro-o-xylene was about 45%based on 94%substrate conversion using sulfuric acid as catalyst when theΦvalue of reaction system was 78.Nitration of o-xylene appeared a good para-selectivity with polyphosphoric acid as catalyst compared with that with sulfuric acid.And the reaction conditions such as concentration of phosphoric acid,temperature and so on were discussed. 4-Nitro-o-xylene could be improved to 65%from 45%based on 80%conversion when employing a equal molar ratio of o-xylene / polyphosphoric acid for 6h at 50℃.The characteristics of the selective oxidation of 4-nitro-o-xylene were studied.The oxidation feature of hydrogen peroxide,nitric acid,ferrate,potassium permanganate and sodium hypochlorite was explored.The experimental results showed that potassium permanganate and sodium hypochlorite oxidation were of good para selectivity.Some reaction parameters such as reaction temperature,reaction time,pH,catalysts etc.were discussed.For a neutral system,the yield of 2-methyl-4-nitrobenzoic acid was 55%when using tetrabutylammonium bromide as phase transfer catalyst,potassium permanganate as oxidant and 4-nitro-o-xylene as precursor.And the yield of 2-methyl-4-nitrobenzoic acid was 53%by using sodium hypochlorite oxidizer and tetrabutylammonium bromide as phase transfer catalyst under proper conditions.