Hydrogen Peroxide → HCID 178510672, compound

Participants

Reaction Conditions

Reaction Steps

3.0 liter of ethylene dichloride solvent & 421.0 gms of 5-amino-3-cyano-1-(2,6-dichloro-4-trifluromethylphenyl)-4-trifluromethylthio pyrazole was charged in a reactor flask with overhead stirring & condenser system. This mass was cooled to a temperature of about 5-10° C. and 2500.0 gms of H2SO4 (85.0% w/w) was added over a period of 3.0 to 4.0 hours. After that, 95.0 gms of H2O2 (50.0% w/w) was added to the aforesaid mass over a period of 3.0 hours at 11-13° C. The reaction temperature was maintained at a temperature of about 12-15° C. for about 2.0 hours with monitoring of reaction conversion. The reaction mass obtained thereafter was slowly added into 1250 ml of chilled water at a 10-20° C. over a period of 2.0 hours. This mass was heated to a temperature of about 60-65° C. to separate the aqueous and organic layers. The organic phase was washed with water & then with 5% NaHCO3 solution, followed by water wash, till a neutral pH was obtained. The crude yield was 436.0 gms. The crude fipronil was then crystallized from same solvent after partial evaporation to yield 358.0 gms crystalline fipronil of 95.0% purity.

Provenance & Evidence