Synthesis method of 4-aminoantipyrine

1. Antipyrine is nitrosated by sodium nitrite, reduced by ammonium bisulfite and ammonium sulfite, hydrolyzed by sulfuric acid, and finally neutralized with liquid ammonia to obtain 4-aminoantipyrine. The process is as follows: Antipyrine is mixed with 50% sulfuric acid to form a solution, which contains 38%-40% antipyrine and 11%-12% sulfuric acid. This solution and sodium nitrite solution were flowed into the nitrosation reactor at the same time, the flow of the two was controlled, the reaction temperature was controlled at 45-50°C, the reaction was stirred, and the end point of the reaction was measured with iodine powder starch test paper to adjust the water flow. The nitroso-antipyrine generated by nitrosation immediately flows into the reduction tank and reacts with the aqueous solution of ammonium bisulfite and ammonium sulfite, which is a reducing agent prepared in the tank. Take a sample to measure the pH value and the degree of reduction. The pH value is between 5.4 and 5.8, and the degree of reduction is about 15 (that is, 1ml of reducing solution consumes the number of milliliters of 0.1N iodine solution). After the reduction, the pH value is adjusted to 5.8-6.0, and the reduction degree is about 5. Raise the temperature to 100°C and hydrolyze for 3h. Cool down to 80°C, neutralize to pH 7-7.5 with liquid ammonia, and stand for stratification. Separate the waste water to obtain 4-aminoantipyrine oil (above 80% content). Press it into a crystallization tank, stir, cool to crystallize, and filter to obtain 4-aminoantipyrine.

2. Antipyrine is nitrosated, then reduced by ammonium bisulfite and ammonium sulfite, hydrolyzed with sulfuric acid, and finally neutralized with liquid ammonia to obtain 4-amino antipyrine.