The general procedure for the synthesis of 4-chloro-3-fluorobenzoic acid from 3-fluoro-4-chlorotoluene and glacial acetic acid was as follows: 99 g of glacial acetic acid, 2.7 g of manganese acetate, and 105 g of 98% sulfuric acid were added to a 20 L autoclave, followed by the addition of 870 g (5.96 mol) of 3-fluoro-4-chlorotoluene of 99% purity. The mixture was stirred and cooled to 15°C, then 215 g of ozone was slowly added (in 10 additions). After completion of the photodissociation process of nitrogen with ozone, the reaction was carried out. Subsequently, the temperature and pressure were adjusted to recover glacial acetic acid, and the layers were separated to ultimately recover 988 g of product to give 4-chloro-3-fluorobenzoic acid with 98.2% purity in about 94.2% yield.
