1-Methylimidazole
1-Chlorohexane
Ethylacetate
Sodium hydroxide
Phosphorus pentoxide
 

See Synthetic Page 747 for experimental setup.

A two-necked round bottomed flask containing 1-methylimidazole (37 mL, 464 mmol) and dry ethyl acetate (37 mL) under nitrogen was cooled in an ice bath. 1-chlorohexane (70 mL, 510  mol)  was added dropwise, with stirring.  Following complete addition, the ice bath was removed and the reaction mixture allowed to warm to room temperature before heating to 60 - 70°C for 11 days. After cooling to room temperature, and while still under nitrogen, the upper layer was decanted using a cannula. Excess 1-chlorohexane was removed from the lower viscous layer by washing with excess toluene. After removal of the solvent and drying at 50°C under high vacuum, the product was obtained as a clear colourless viscous oil (71.6%)

1. Careful distillation of the starting materials, 1-methylimidazole and 1-chlorohexane, from an appropriate drying agent (KOH for 1-methylimidazole, P₂O₅ for 1-chlorohexane). Store distilled materials under an inert atmosphere and use canula or syringe apparatus to transfer them into the reaction vessel.

2. Oven and vacuum drying of glassware prior to reaction. Ensure reaction vessel is closed, and glass joints are tight-fitting (avoid grease) to ensure an inert atmosphere.

3. Higher temperatures (shorter reaction time) leads to a coloured product and tedious purification.

4. After 11 days and an initial toluene wash 1-methylimidazole (14%) was detected in the product as judged by HNMR.

5. Removing 1-methylimidazole via repeated washing with toluene proved tedious, requiring vigorous stirring with excess solvent overnight and assesment by HNMR.

6. To avoid using excess toluene,  dry ethyl acetate may prove to be a suitable alternative. 

7. The product may appear as a semi-solid after repeated washes.


 

¹HNMR (400 MHz, DMSO-d6) δH 9.38 (1H, s), 7.84 (1H, s), 7.77 (1H, s), 4.18 (2H, t), 3.87 (3H, s), 1.78 (2H, quintet), 1.30-1.21 (6H, m), 0.86 (3H, t). 

¹³CNMR (101 MHz, DMSO-d6) δC 137.22, 124.03, 122.73, 49.12, 36.16, 31.03, 29.86, 25.61, 22.34, 14.28.

m/z 167 ([C₆C₁im]⁺, 100%), 83, 37, 35 (Cl^-, 100%).