4-Hydrazinobenzoic acid hydrochloride

To 600 ml beaker add water 150 ml, stirring, add p-aminobenzoic acid 27.4 g, 10N hydrochloric acid 57.5 ml, after cooling the solution to 0 , slowly add sodium nitrite solution (from 15 grams of sodium nitrite and 30 ml of water to formulate), add the end of the system, adjust the system pH for 1-2, control the temperature of the reaction system 5 , the reaction for 20 minutes, filtration and retention of the filtrate. Add 200 ml of water to a 1000 ml beaker, add 64 g of sodium metabisulfite and 78 g of sodium hydroxide with stirring, at this time, the solution pH was 7, the solution temperature was 35 C. After the solution was cooled down to 15-18 C, the above filtrate was added slowly, and the temperature of the solution was 20 C when it was added, the pH was 7, and the reaction was carried out for 30 minutes, and then the temperature was raised to 50-60 C, and 115 ml of hydrochloric acid was added to it, and the temperature continued to be raised to 97-100 C, and the reaction was continued to be carried out for 20 minutes. Elevate the temperature to 97-100 C, and at this temperature reaction for 30 minutes after adding 7 grams of activated carbon, decolorization after 90 C filtration to retain the filtrate, cooled to 15 C, add hydrochloric acid, the material precipitation, filtration, pumping dry to get the 4-carboxyphenylhydrazine hydrochloride product. The purity of 4-carboxyphenylhydrazine hydrochloride was 98.92% as measured by high performance liquid chromatography.