Hydrogen Bromide → 2-Bromobenzimidazole

Participants

Reaction Steps

To a flask were added 24 ml 48% hydrobromic acid and 120 ml methanol. The mixture was cooled to 5 C and 10 g 2-mercaptobenzimidazole was added. Maintaining a temperature of less than 10 C, 41.5 g of bromine were added in small portions. The mixture was allowed to warm to 22 C, and stirred for 16 hours under nitrogen. After cooling to 5 C, the solid was filtered and then added to 50 ml methanol containing 20 ml aqueous ammonium hydroxide. The pH was adjusted to 6.5 with acetic acid, and the mixture was cooled to 5 C. The product was filtered and washed with water, and dried. A second crop was obtained by cooling the filtrates which was filtered, washed with water and dried. The combined crops resulted in 9.05 g of a solid.

Provenance & Evidence