Abstract: A new compound 1, 5-amino-1-2, 6-dichloro-4-(trifluoromethyl) phenyl-4-(trifluoromethyl) sulfinyl -1H -pyrazole -3-carboxylic acid has been produced by hydrothermal reaction of fipronil (5 -amino -1 -2, 6-dichloro-4-(trifluoromethyl) phenyl-4-(trifluoromethyl) sulfinyl-1H-pyrazole-3-nitrile) and lewis acid ZnCl₂. The compound was characterized by elemental analysis, IR spectra, and single-crystal X-ray diffraction. The crystal belongs to the monoclinic system, space group P2₁/c with a = 12.7457(8)Å, b = 8.8244(6)Å, c = 15.7322 (11)Å, α= 90°, β = 100.2310(10)°, γ=90°, Z= 4, V = 1741.3(2)ų, F(000) = 856. The intermolecular hydrogen bonds are speculated to hold together the molecules of the compound. UV spectrum of 1 in solid state shows two maximum absorption peaks at 220 and 281 nm respectively.