Sulfuric Acid → 4-Bromo-2-thiophenecarboxylic Acid

Participants

Reaction Conditions

Reaction Steps

Chromium (VI) oxide (20 g), and concentrated sulfuric acid (32 g) were dissolved in water (50 mL) and when dissolution was complete, the volume was made up to 100 mL with water. 55 mL of the resulting solution was added dropwise to a solution of 4-bromothiophene-2-carboxaldehyde (19.1 g) in acetone (200 mL) stirred at 0° C. After 2 h, the solution was diluted with water and extracted with chloroform. The organic extracts were washed with water, then extracted with aqueous sodium hydroxide. The alkaline mixture was acidified by cautious addition of concentrated hydrochloric acid then extracted with chloroform. The organic layer was then dried (Mg2SO4), filtered, and evaporated. The resulting solid was recrystallised from diethyl ether/hexane to give a colourless solid; MS (ES+) 207, 209 (MH+).

Provenance & Evidence