Hydrochloric Acid → 1,3-Diisopropylimidazolium chloride

Participants

Reaction Conditions

Reaction Steps

Propylamine, 17.73 grams (0.3 mol), was added dropwise over 20 min. to a suspension of paraformaldehyde, 9.01 grams (0.3 mol), in 50 ml of toluene at such a rate that the temperature did not exceed 40° C. When the addition was complete, the mixture was stirred for an additional 10 min. The mixture was then cooled at 4° C. by means of an ice bath. Propylamine, 17.73 grams (0.3 mol), was added in a slow steady stream to the cooled mixture. When the second isopropylamine addition was complete, 50 ml of aqueous 6N HCl (0.3 mol) was added dropwise over 30 min. to the reaction mixture. By means of an ice bath, the reaction temperature was held below 25° C. When the HCl addition was complete, the ice bath was removed and the solution was warmed to 25° C. At this temperature, 43.53 grams (0.3 mol) of 40% aqueous glyoxal was added. When the glyoxal addition was complete the reaction mixture was stirred for an additional 1 h. An additional 45 ml of toluene was added to the reaction mixture and water, 78.18 grams, was removed from the reaction mixture by azeotropic distillation (Dean Stark trap) with the toluene. Removal of volatiles under vacuum yielded 58.02 grams (102% of theory) of 1,3-diisopropylimidazolium chloride. 1H NMR (CD3CN) of the material showed only resonances at δ 0.90 (t, 3JHH =7.4 Hz, 6 H); 1.88 (tt, 4 H); 4.27 (t, 3JHH =7.4 Hz, 4 H); 7.75 (d, 4JHH =1.6 Hz, 2 H); 9.47 (t, 4JHH, =1.6 Hz, 1 H) consistent with the desired product.

Provenance & Evidence