4-Fluorophenylhydrazine hydrochloride

371-40-4

823-85-8

The general procedure for the synthesis of 4-fluorophenylhydrazine hydrochloride from 4-fluoroaniline was as follows: 4-fluoroaniline (127.6 g, 1 mol) was dissolved in concentrated hydrochloric acid (293 mL) and stirred for 2 hours at room temperature. Subsequently, the above solution was slowly added dropwise to a solution of sodium nitrite (72.5 g, 1.05 mol) in water (145 mL) at a temperature controlled below 5 °C. After the dropwise addition, stirring was continued for 1 hour, and then the filtrate was separated by filtration to obtain the filtrate. A solution of NaHSO3 (213.2 g, 2.05 mol) in water (500 mL) was slowly added dropwise to the filtrate over a temperature range of 0-10 °C while the pH was adjusted with 25% NaOH solution to maintain between 6-7. The reaction mixture was heated to 80 °C and maintained at this temperature for 1 hour. Upon completion of the reaction, the mixture was cooled to room temperature and then concentrated hydrochloric acid (600 mL) was added dropwise. Next, the mixture was heated to 90-100°C for 1 hour. Finally, the mixture was cooled to 10 °C and the precipitate was collected by filtration to give the light red solid product 4-fluorophenylhydrazine hydrochloride (129.3 g, 60% yield).