In a 1L Schlenk flask, 92.1 g (1.20 mol) of N-methylimidazole was mixed with 261.5 g (2.40 mol) of ethyl bromide and 302.3 g (1.80 mol) of sodium hexafluorophosphate, and the reaction was stirred at 70°C for about 2 weeks. Upon completion of the reaction, a white solid was obtained by filtration through a protective gas glassware. The filter cake was washed twice with 400 ml of dichloromethane, the organic phases were combined and the dichloromethane was evaporated. Subsequently, the white solid was dried overnight at 60 °C under high vacuum (HV) to give 1-ethyl-3-methylimidazole hexafluorophosphate in 92% yield. For qualitative detection of residual chlorides, about 1 g of the product was dissolved in about 5 ml of water, acidified by adding 2 drops of concentrated nitric acid, followed by the addition of 3-4 drops of silver nitrate solution, and observed to see if a silver chloride precipitate was generated. The absence of precipitate indicates that there is no chloride residue in the product. The product characterization data are as follows: 1H NMR (300 MHz, CDCl3): δ=9.6 ppm (s, 1H, Ha); δ=7.26 ppm (d, 1H, Hc); δ=7.24 ppm (d, 1H, Hd); δ=3.9 ppm (q, 2H, He); δ=3.6 ppm (s, 3H, Hb); δ=1.2 ppm ( t, 3H, Hf).13C-NMR (75 MHz, CDCl3): δ=137 ppm (C1); δ=124-122 ppm (C3, C4); δ=45 ppm (C5); δ=36 ppm (C2); δ=16 ppm (C6).31P-NMR (121 MHz): -143.08 (heptet, J=710 Hz). J=710 Hz).19F-NMR (281 MHz): -72.5 (d, J=710 Hz).
