Water → 6-Fluoronicotinic Acid

Participants

Reaction Conditions

Reaction Steps

A solution of the 2-fluoro-5-methylpyridine (30 g) in water (1.2 L) was stirred with a mechanical stirrer, potassium permanganate (100 g) was added in portions and the mixture heated to 100° C. When the characteristic purple color of the mixture faded to black, another portion of potassium permanganate (50 g) was added and the mixture was then stirred at 100° C. for 4.5 hours. The mixture was filtered hot, the filtrate was cooled and extracted with ether to remove unreacted starting material. The aqueous layer was neutralized to pH 7 with concentrated HCl and concentrated to a volume of 350 mL. The pH was lowered by addition of concentrated HCl to pH 4-2 at which point a large amount of precipitate appeared. The precipitate was filtered and the aqueous layer was extracted with ethyl acetate (500 mL). The organic layer was dried, evaporated, and the solids combined to give 2-fluoropyridine-5-carboxylic acid (17.1 g) as a colorless solid having a melting point of 275°-278° C.

Provenance & Evidence