How is 1-Octyl-3-methylimidazolium hydrogen sulfate (CAS: 497258-85-2) typically synthesized?

1-Octyl-3-methylimidazolium hydrogen sulfate is typically synthesized by the reaction of 1-octylimidazolium bromide with sodium bisulfate in an aqueous medium. The synthesis involves the substitution of bromine by hydrogen sulfate, which is catalyzed by a base such as sodium hydroxide. The process yields a high purity product with a selectivity of over 95%, and the overall yield can reach up to 85%.