Hydrochloric Acid → 2-[p-Carboxyphenyl]-5,6-diaminobenzimidazole hydrochloride

Participants

Reaction Steps

A solution of 5 g (16.7 mmole) of 2-[p-carboxyphenyl]-5,6-dinitrobenzimidazole (as prepared in Example I) in 200 ml of methanol at 0° C was thoroughly purged with nitrogen. To this was added 500 mg of 10% palladium on charcoal, and 30 ml of concentrated HCl. The hydrogenation flask was then pressurized with 55 lbs/in2 of hydrogen, and the flask was shaken at room temperature for 8 hours. After the reaction period had elapsed, the solution was filtered by suction, and the filtrate evaporated to dryness in vacuo. The residual yellow solid was redissolved in a minimum amount of boiling methanol (which contained a trace of HCl), and the filtered solution added to 50 ml of concentrated HCl. Removal of the methanol from the solution in vacuo and subsequent cooling in ice yielded 4.2 g (82%) of 2-[p-carboxyphenyl]-5,6-diaminobenzimidazole hydrochloride as fluffy yellow needles.

Provenance & Evidence