2-Fluoro-4-nitrophenol

367-12-4

7440-44-0

1526-17-6

403-19-0

A. Synthesis of 2-fluoro-4-nitrophenol 2-Fluorophenol (32.3 g, 0.288 mol) was dissolved in dichloromethane under ice-salt bath conditions and cooled to -10 °C. 90% nitric acid (22 g, 0.31 mol HNO3) was added slowly, and the titration rate was controlled to maintain the reaction temperature at about -5 °C, and the titration process lasted for 1 hour. After completion of the dropwise addition, the reaction mixture was continued to be stirred at 0°C for 1 hour. At the end of the reaction, the precipitate was collected by filtration and washed several times with cold dichloromethane. Analysis by GC and thin layer chromatography (silica gel, 7:3 hexane-acetone) showed that the product was mainly a single compound and the by-products generated in the reaction were of low polarity and volatility. The solid was dissolved in ether, washed with water, dried over anhydrous magnesium sulfate, and the solvent evaporated. The resulting solid was recrystallized with methylcyclohexane to give 13 g of a pale yellow solid with a melting point of 119°-121°C. Nuclear magnetic resonance (CDCl3) analysis confirmed that the product was 2-fluoro-4-nitrophenol. B. Isolation of 2-fluoro-6-nitrophenol The dichloromethane mother liquor was washed with water, dried over anhydrous magnesium sulfate and the solvent was evaporated. The resulting solid was ground with boiling hexane (3 x 150 ml) to effectively remove the least polar and volatile by-products. The hexane solution was treated with activated carbon, filtered and concentrated to about 300 ml, and cooled to give 13.5 g (30% yield) of 2-fluoro-6-nitrophenol as a yellow solid with a melting point of 70°-86° C. The solid was then dried with water.