Synthesis, structure, and reactivity of sulfonated imidazole compounds

ORGN 130

Andrew P Purdy,, Justin Luther1, and Richard Gilardi, (1) Chemistry Division, Naval Research Laboratory, Code 6125, 4555 Overlook Av, SE, Washington, DC 20375-5342, (2) LSM 6030, Naval Research Laboratory
Oleum (27% SO3) (59 mL) and 2-ethyl-4-methyl-imidazole (36 g) were stirred at 125 C for 1 h. The reaction mixture was poured into water and boiled with stirring, while BaCO3 was slowly added to neutralize the acid. The Ba salt of the sulfonated imidazole was isolated by filtration from the voluminous precipitate, and reacidified with H2SO4 to precipitate all the Ba, and filtered again. After rotary evaporation 2-ethyl-4-methyl-imidazole-5-sulfonic acid (42 g, 67%) was recrystallized from MeOH/ H2O. The compound crystallized in a herringbone type layered structure held together with hydrogen bonding. A related compound, 2-methyl-imidazole-4-sulfonic acid had a similar H-bonded structure. The reaction of the Ag and K salts of these sulfonic acids with alkyl dihalides and ditosylates were investigated as a means of preparing polymeric materials.