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EXAMPLE 3 50 g of 3,4-dichloro-5-nitro-benzotrifluoride and 5 g of benzyltriethylammonium bromide are initially introduced into 150 ml of methanol, and 100 g of 50% strength sodium hydroxide solution are added dropwise at 25 to 30 C. The mixture is then stirred at 65 C. for a further 4 hours and cooled, 100 ml of water are added and the mixture is rendered acid with sulphuric acid. The crude product is extracted with methylene chloride, the solution is dried and the methylene chloride is distilled off. The residue is subjected to fractional distillation and 35 g of 2-chloro-4-trifluoromethyl-6-nitrophenol with a boiling point of 74 to 76 C. under 0.25 mm are obtained. Melting point: 33-34 C. from hexane. Yield: 77% of theory.