由邻硝基甲苯合成邻氨基苯甲酸

College of Chemistry and Molecular Science,Wuhan UniversityReport of Organic Chemistry ExperimentDesigned Experiment：Synthesis of 2-Aminobenzoic Acidfrom 2-NitrotolueneTutor: Ying XiongStudent’s Name: Wenxin LuMajor: Chemistry Class of Hongyi SchoolStudent ID: 2012301040179Date: Apr. 24th to May 29th, 2014(5 weeks in total, once a week)Ⅰ. Purpose of the Experiment1. Initiate the progress of the syntheses with the raw material, 2-nitrotoluene, to prepare the important organic synthetic raw material, 2-aminobenzoic acid, by the oxidation of potassium permanganate and the reduction of Fe/HCl.2. Learn to use IR and 1HNMR to analysis and represent the intermediate and product, determine the purity and the structure of them.3. Review some operations in fundamental organic chemistry experiment, such as reflux, simple distillation and recrystallization.4. Know the common oxidation and reduction methods in organic synthesis, to strengthen the basis of theoretical study.5. By comparing different synthesis methods, determine a simple one which has a characteristic of high yield and less pollution, to understand the idea of “Green Chemistry”.Ⅱ. Principle of the Experiment2-Aminobenzoic acid is an indispensable organic synthetic raw material and intermediate. In the aspect of dye, it is used to prepare anthraquinone dyes, azo dyes and indigoiddyes, in the aspect of medicine, it is used to make pontal, pyrozoline, benzydamine, tardan, etc. 2-Aminobenzoic acid is also used in organic synthesis, for example, to prepare compound like 3-hydroxyindole and methyl anthranilate. As a chemistry reagent, it is used to test cerium, cadmium, cobalt, copper, lead, magnesium, mercury, nickel, nitrite, palladium, zinc, silver and uranium.Step 1: Oxidation of 2-Nitrotoluene2-nitrotoluene is a derivative of arene, which has an nitryl and an adjacent methyl on benzene ring. There are some α-H atoms on the C atom directly attached to benzene ring, which can be oxidized to a carboxyl group by many kinds of oxidation.There are various methods of preparing 2-nitrobenzoic acid from 2-nitrotoluene, and several of them are widely applied [1]:(1)Potassium permanganate method. The advantages of this methodare that the yield is as high as 80%, the oxidizing progress is fast, and the operation is easy, whereas, it has weaknesses of low selectivity, high cost and much waste. (2)Sodium dichromate method. 2-nitrobenzoic acid can be prepared by mixing 2-nitrotoluene, sodium dichromate and sulfuric acid in water and keep them slightly boiling for half an hour. The cost of this method is lower than (1), but its yield is inferior to that, moreover, the chromium(Ⅲ) ion produced is severely harmful to environment. So this method is gradually abandoned. (3)Nitric acid oxidizing method. The reduzate of nitric acid is gas and easy to separated, meanwhile, no heavy mental ion is generated. But the using of nitric acid will make picric acid mixed in the product which amount cannot be ignored, regardless of the concentration of nitric acid. Also, nitric acid is corrosive to the facility, so this method can hardly be popularized now. (4)Sodium hypochlorite method. Expensive ruthenium tetroxide will be used in this method, restricted by the condition of the experiment, this method can’t be used. (5)The method of air liquid phase oxidation. This is the most potential and attractive method nowadays, restricted by the condition of the experiment, this method can’t be used.Comprehensively considering the condition of this experience, the author will adopt the potassium permanganate method to prepare 2-nitrobenzoic acid from 2-nitrotoluene:Step 2: Reduction of 2-Nitrobenzoic Acid2-Nitrobenzoic acid is a kind of aromatic nitro compound, which nitryl on the benzene ring can be reduced to amino by reductant.There are also many ways to reduct aromatic nitro compound to arylamine[2]: (1)Catalytic hydrogenation by using Pd-C catalysis. NaBH4 is a substitute. The reaction is easy to proceed and to be controlled due to its gently extent, and its yield is considerable. But the Pd-C catalysis is not available on the condition of this experiment. (2)Hydrazine reduction. Mix 2-nitrobenzoic acid, methyl alcohol, solution of sodium hydroxide and Raney-Ni, heat to reflux, then drop hydrazine into the system, continue to reflux, high-yield 2-aminobenzoic acid will be gained. (3)Zn-NH4Cl method. In this method, barium 2-aminobenzoate is reacted initially with zinc and ammonium chloride, then with alcohol solution of potassium hydroxide, 2-aminobenzoic acid will be gained.(4)Electrolysis reduction. Use lead, tin or zinc amalgam to electrolyze 2-nitrobenzoic acid, then high yield of 2-aminobenzoic acid will be generated even without catalysis. (5)[3]Fe/HCl or Fe/HOAc reduction. If hydrochloric acid and iron powder are used as reductant, 2-nitrobenzoic acid can be reduced to 2-aminobenzoic acid within 3 hours. Besides, tin chloride (specificity reductant) and lithium aluminum hydride (strong reductant) can be used, but tin salts are toxic and lithium aluminum hydride is inflammable in wet air, so they are both abandoned.The synthesis methods above are mostly aimed to 4-nitro compound, while the report of synthesis of 2-aminobenzoic acid is relatively less. Considering the similarity between 2-nitrotoluene and 4-nitrotoluene, the author will use the synthesis method of 4-aminobenzoic acid for reference to synthesize 2-aminobenzoic acid. Fe/HCl reduction is adopted in this experiment to reduce 2-nitrobenzoic acid to 2-aminobenzoic acid:Recrystallization重结晶是提纯物质的一种实验方法，有两种方式：单一溶剂法和混合溶剂法。