Synthesis of benzimidazolium hydrobromide. The synthesis follows the same strategy of an acid-base salt as for benzimidazolium hydrochloride. Benzimidazole (8.671 g, 73.4 mmol) was dissolved in 25 mL demineralized water in a beaker, followed by the addition of 48% hydrobromic acid (13.686 g, 81.2 mmol) with stirring. The solutions were heated to 110 °C in an oil bath until all liquid had evaporated, resulting in the formation of brown crystalline powder.