To obtain a new compound useful as a synthetic intermediate for 2,3,5,6-tetrafluoro-benzoic acid which is an intermediate product of a highly effective insecticide.

This new 4-trifluoromethyl-benzoyl compound is new 2,3,5,6- tetrachloro-4-trifluoromethyl-benzoyl chloride and new 2,3,5,6-tetrafluoro-4- trifluoromethyl-benzoyl fluoride. The compounds are obtained by chlorinating 4-trifluoromethyl-benzoyl fluoride in the presence of chlorosulfonic acid in a solvent (e.g. carbon terachloride) at <60°C temperature to form the 2,3,5,6- tetrachloro-4-trifluoromethyl-benzoyl chloride, which is then fluorinated in an aprotic dipolar inert solvent (e.g. tetramethylene sulfone) using potassium fluoride at 50-190°C to thereby afford the 2,3,5,6-tetrafluoro-4-trifluoromethyl-benzoyl fluoride.