19763-90-7

white to light yellow crystal powde

The general procedure for the synthesis of 3,4-dichlorophenylhydrazine hydrochloride from 3,4-dichloroaniline is as follows: (A) In a 1000 ml three-necked flask, 3,4-dichloroaniline (64.8 g), 200 ml of concentrated hydrochloric acid, and 100 ml of water were added, heated to 80 °C and mechanically stirred at high speed for 40 min until a slurry was formed. The slurry was transferred to a 1000 mL beaker and cooled in an ice bath to a temperature below 5°C. In another 100 mL beaker, sodium nitrite (31.2 g) and 50 mL of water were added, stirred to dissolve, and similarly cooled in an ice bath to a temperature below 5 °C. The sodium nitrite solution was slowly added to the slurry and the temperature was maintained at 5°C for 1 h. The diazonium salt solution was obtained by filtration and transferred to a 2000 ml beaker. Another 250 ml beaker was taken and 200 ml of concentrated hydrochloric acid and stannous chloride dihydrate (188 g) were added and stirred to dissolve. The hydrochloric acid solution of stannous chloride dihydrate was slowly added to the diazonium salt solution through a thermostatic funnel. The temperature was adjusted to 25°C and stirred with a mechanical stirrer for 1 h. The yellow powder was obtained by filtration. The yellow powder was added to 80°C water, stirred to dissolve and then filtered, cooled to crystallize and filtered again to obtain white needle-like crystals. The temperature of the remaining filtrate was adjusted to 50°C, concentrated by rotary evaporation, and cooled to obtain white powder. Combine the white needle-like crystals and white powder, wash with dilute hydrochloric acid, filter and dry to obtain white solid powder 3,4-dichlorophenylhydrazine hydrochloride (72.6 g).

[1] Angewandte Chemie - International Edition, 2013, vol. 52, # 47, p. 12426 - 12429
[2] Angew. Chem., 2013, vol. 125, # 47, p. 12652 - 12656,4
[3] Journal of Organic Chemistry, 2014, vol. 79, # 5, p. 2314 - 2320
[4] Patent: CN107915677, 2018, A. Location in patent: Paragraph 0013; 0014