Acetic Acid → 3-[2-Chloro-4-(trifluoromethyl)phenoxy]benzoic acid

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Into a three liter flask is added 1.3 liters of acetic acid, 614 g. (1.90 mole) of 88.8% pure 3-(2-chloro-4-trifluoromethylphenoxy)toluene, and 32.0 g. (0.128 mole) of cobalt acetate tetrahydrate. To this stirred pink solution is added 20.0 ml (0.173 mole) of 47% aqueous hydrogen bromide whereupon the solution turns blue. The solution is then heated to 90° C. and a flow of oxygen (100%, 2.19×10-2 mole/min) is initiated. Hydrogen peroxide 10.0 ml (30%, 0.088 mole) is then added via a syringe to the solution and the exotherm raises the reaction temperature to 98° C. within 5 minutes. The reaction is monitored by thin layer chromatography and is complete within 4 hours. Isolation of the oxidation product 3-(2-chloro-4-trifluoromethylphenoxy)benzoic acid from the reaction mixture is accomplished by distillation of the acetic acid solvent, neutralization with aqueous sodium hydroxide to a pH of 11, filtration to remove the insoluble cobalt hydroxides and acidification of the filtrate with sulfuric acid to precipitate the product, which is filtered and dried to give 680.3 g of 85.1% 3-(2-chloro-4-trifluoromethylphenoxy)benzoic acid. This represents of 96.1% yield of this product based on the 3-(2-chloro-4-trifluoromethylphenoxy)toluene starting material.

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