2-Fluoro-3-nitrobenzoic acid is an important raw material and intermediate used in organic synthesis, pharmaceuticals, agrochemicals and dyestuff.
Concentrated sulfuric acid (195 ml) was added carefully and stirred to a solution of 2-fluoro-3-nitrotoluene (100 g, 645 mmol) in acetic acid (1000 ml). The mixture was warmed up to 95° C. The chromium trioxide solution (226 g, 2.25 mol) in water (200 ml) was added dropwise while stirring for over 2 h. After addition, the mixture was heated by stirring for another 3 h, allowed to cool down to room temperature, and poured into water (3 L). The mixture was extracted with ethyl acetate (3.x.1 L), the combined organic layers were dried over Na2SO4and concentrated under reduced pressure to afford a light green solid, which was washed with dichloromethane (3.x.300 ml) and dried under vacuum to afford 2-Fluoro-3-nitrobenzoic acid was obtained as a light yellow solid (75 g, 62.8percent). 1H NMR (300 MHz, DMSO) δ ppm 8.27 (m, 1H), 8.15 (m, 1H), 7.48 (m, 1H).
