(1) Diazotization: 3-bromoaniline and 37% concentrated hydrochloric acid were mixed and cooled to 0-5, 35% aqueous sodium nitrite was added while stirring, and the temperature was maintained at 0-5 for 1-1.5 hours.
(2) reduction: add 37% concentrated hydrochloric acid, water and zinc powder in the reaction solution, keep the temperature between 15-20 reaction until the reaction is complete, the reaction solution becomes grayish-white, and then add 20-30% sodium hydroxide solution to the reaction solution PH 10, 5 holding time of 1-2 hours, precipitate crystals, filtered to get the crude 3-bromophenylhydrazine.
(3) purification: 3-bromophenylhydrazine crude dissolved in water, heated to 60 C to make it completely dissolved, and then add an appropriate amount of activated carbon decolorization for 20 minutes, hot filtration of colorless filtrate, 5 C holding time of 1 ~ 2 hours, precipitation of crystals, filtration of 3-bromophenylhydrazine pure product.
(4) Salt formation: 3-bromophenylhydrazine pure product dissolved in 37% hydrochloric acid, stirring at 60 ~ 70 until the reaction solution precipitated crystals, cooled to 20 , filtration, acetone drenching the filter cake, drying that is, 3-bromophenylhydrazine hydrochloride finished product.
