One Step Oxidation Of Nitrobenzyl Chloride To Synthesize Nitrobenzoic Acid

The o-Nitrobenzoic acid(ONBA),m-Nitrobenzoic acid(MNBA),p-Nitrobenzoic acid(PNBA)are important intermediates in the field of dyestuff,pigment and medicine.Traditional methods of synthesizing above three nitro benzoic acids were by oxidation of nitrotoluene with chemical oxidants or air.The chemical oxidants include potassium permanganate,sodium dichromate,and nitric acid.A lot of heavy metal oxides,heavy metal salts,or waste acid are generated with chemical oxidation,which causes serious pollution.The catalytic air oxidation conditions are harsh,requiring high temperature,high pressure,and special catalysts.In this study,nitrobenzyl chlorides were used as raw material and sodium hypochlorite solution was used as oxidant,and nitrobenzoic acids were prepared by one-step oxidation reaction.The effect of the molar ratio of reactants,the amount of Na OH,the reaction time,the reaction temperature and the choice of solvent on the yield of nitrobenzoic acid were investigated in the experiment,and the optimal synthesis process conditions were finally determined.The optimal synthesis process of o-Nitrobenzoic acid was: the molar ratio of o-Nitrobenzyl chloride,Na OH and sodium hypochlorite was 1:1:3,the reaction time was 3.0 h,and the reaction temperature was 100～105 ℃.The optimal synthesis process of m-Nitrobenzoic acid was: the molar ratio of m-Nitrobenzyl chloride,Na OH and sodium hypochlorite was1:1.5:2,the reaction time was 3.1 h,and the reaction temperature was 90～95 ℃.The optimal synthesis process of p-Nitrobenzoic acid was: the molar ratio of p-Nitrobenzyl chloride,Na OH and sodium hypochlorite was 1:1.5:2,the reaction time was 2.5 h,and the reaction temperature was 90～95 ℃.Three kinds of target products were washed with petroleum ether reagent,extracted with normal hexane reagent and then vacuum filtered.The o-Nitrobenzoic acid,m-Nitrobenzoic acid and p-Nitrobenzoic acid were obtained in the yield of 81.1%,96.1% and 98.3%respectively.They were characterized by nuclear magnetic resonance,high performance liquid chromatography,infrared spectroscopy,elemental determination analysis,thin layer chromatography analysis,and melting point determination.The research shows that nitrobenzoic acids were prepared by one-step oxidation of nitrobenzyl chloride with sodium hypochlorite,which avoids the environmental pollution of metal oxidants,the high temperature and high pressure of air oxidation.It is a green oxidation process with great potential.