1-Ethyl-3-methylimidazolium tetrafluoroborate

Light yellow liquid

In einen 1 I Schlenkkolben werden 114, 5 g (1, 39 mol) 1-Methylimidazol, 304, 0 g (2, 79 mol) Ethylbromid und 228, 9 g (2, 09 mol) Natriumtetrafluorborat gegeben und bei 70C ca. 2 Wochen geruehrt. Der entstandene weisse Feststoff wird ueber eine Schutzgasfritte abfiltriert und die sich gebildeten zwei Phasen voneinander mit Hilfe eines Scheidetrichters getrennt. Die untere gelbliche Phase wird ueber Nacht bei 60C im HV getrocknet. Man erhaelt 1-Ethyl-3-methylimidazoliumtetrafluoroborat in 87 %iger Ausbeute. Zum qualitativen Nachweis auf Chloridreste, werden ca. 1 ml des Produktes mit ca. 5 ml Wasser versetzt und mit 2 Tropfen konzentrierter Salpetersaeure angesaeuert. Zu dieser Loesung werden dann ca. 3-4 Tropfen Silbernitrat gegeben um etwaig vorhandenes Chlorid als Silberchlorid auszufaellen. Das Ausbleiben eines Niederschlags spricht fuer die komplette Abwesenheit von Chloridresten. 1H-NMR (300 MHz, CDCl3):delta=9.6 ppm (s, 1H, Ha); delta=7.26 ppm (d, 1H, Hc); delta=7.24 ppm (d, 1H, Hd); delta=3.9 ppm (q, 2H, He); delta=3, 6 ppm (s, 3H, Hb); delta=1.2 ppm (t, 3H, Hf). 13C-NMR (75 MHz, CDCl3):delta=137 ppm (C1); delta=124-122 ppm (C3, C4); delta=45 ppm (C5); delta=36 ppm (C2); delta=16 ppm (C6). 19F-NMR (281 MHz, CDCl3):delta= -151, 3 ppm (d, 1J(BF)= 22 Hz)General procedure: A mixture of the appropriate imidazolium bromide (0.2 mol) and hex-1-ene (30 mL) was stirred in a flask, and a mixture of the appropriate protonic acid (0.2 mol) and H2O2 (0.1 mol) was added dropwise at room temperature (25 C). After the appropriate time (Table 1), the liquid was placed in a separatory funnel and the oil phase was removed. The aqueous phase was washed with portions of CH2Cl2 (50mL) until it was colorless. Residual H2O in the product was removed by azeotropic distillation with cyclohexane. For [BzMim]PF6 (Table 1, entry 18), which has low water solubility, post-processing required only distillation and desiccation of the oil phase.(2) mixing the quaternary ammonium salt solution obtained in the step (1) with sodium tetrafluoroborate (the molar ratio of 1-methylimidazole to sodium tetrafluoroborate is 1:1), After heating to 40 C, Under agitation, Irradiation with ultraviolet light of 600 W/m2, The exposure time is 18h, a mixed solution containing a tetrafluoroborate ionic liquid; (3) filtering the mixture obtained in the step (2) twice, Get the filtrate, The filtrate was concentrated at 60 C. Remove ethanol, Obtaining Tetraethyl silicate (156.25 g, 0.75 mol), 1-methylimidazole (41.05 g, 0.5 mol), 150 mL of DMSO was added to the autoclave, stirred, and reacted at about 110 C for 7 h.After the reaction was completed, the desolvent was evaporated to give 186.25 g of a thick layer.1-methyl-3-ethylimidazolium quaternary ammonium salt.A 40% aqueous solution of tetrafluoroboric acid (164.63 g, 0.75 mol) was added dropwise to the 1-methyl-3-ethylimidazolium quaternary ammonium salt, and the reaction was stirred for 0.5 hour.After the completion of the reaction, the reaction mixture was turbid and cooled to crystallize, and the solid was filtered off with suction. The filtrate was evaporated to remove solvent and water to give crude product 97.86 g, yield 98.9%.The crude product was recrystallized from 250 mL of anhydrous methanol to give 81.24 g of high-purity 1-methyl-3-ethylimidazolium tetrafluoroborate in a yield of 82.1%.The yield is calculated on the basis of the amount of 1-methylimidazole, and there is also a product in the filtrate.1-Methylimidazole (82.10 g, 1 mol) was placed in a three-necked flask.40% aqueous solution of tetrafluoroboric acid (263.43 g, 1.2 mol) was added dropwise.After the reaction is over, Add azeotropic dehydration with 200 mL of toluene.192.46 g of N-methylpyrrole tetrafluoroborate were obtained.1-methylimidazolium tetrafluoroborate 192.46g, Diethyl carbonate (236.26 g, 2 mol), 160 mL of methanol was added to the autoclave, Stir, The reaction was carried out at 135 C for 8 h.After the reaction is over, Cooling crystals, Filtering, 194.94g of crude 1-methyl-3-ethylimidazolium tetrafluoroborate, The yield was 98.5%.Recrystallized from 250 mL anhydrous methanol, Obtaining 168.82 g of high purity 1-methyl-3-ethylimidazolium tetrafluoroborate, The yield is 85.3%In a round bottomflask, a mixture of 1-methyl imidazole (4.1 g; 50 mmol) andethyl bromide (5.45 g, 50 mmol) was stirred at 80 C in neatcondition for 10 h. After that, neutral ionic liquid [EMIM][Br]was obtained as white solid. The reactionmixturewaswashedwith ethyl acetate four times for complete removal of n-ethylbromide and other organic compounds. It was then subjected to vacuum to obtain the pure solid [EMIM][Br]. After that, sodium tetrafluoroborate (5.3 g, 48.17 mmol) was added tothe [EMIM][Br] in acetone and stirred overnight at roomtemperature to obtain [EMIM][BF4]. The solution was filteredand acetone was removed in vacuum to obtain the pure[EMIM][BF4] as a colorless liquid.General procedure: Another anion exchange reaction was carried out to achieve IL with boron tetrafluorides as a counter anion (IL-BF4) by metathesis reaction as per reported literature with minor modifications (Scheme 2). A demonstrative example for the synthesis of [RMIM]BF4 (i.e., [EMIM]BF4, [BMIM]BF4, [HMIM]BF4, [OMIM]BF4, [DMIM]BF4) and [RBZMIM]BF4 (i.e., [EBZMIM]BF4, [BBZMIM]BF4, [HBZMIM]BF4, [OBZMIM]BF4, [DBZMIM]BF4) in Scheme 2 (step-3) derivatives are as follows: 1:2 ratio of the 1-methyl-3-alkylimidazolium bromide or 1-methyl-3-alkylbenzimidazolium bromide ([RBZMIM]Br) and NaBF4 were added distinctly in to the round bottom flask containing 25mL of methanol and stirred at room temperature for 24h. Afterward, the salt was removed by filtering the reaction mixture using Whatman filter paper. Further, the filtrate was centrifuged for 10min at 3000rpm to isolate the residual salts. Solvent was evaporated under reduced pressure, vacuum dried and characterized (using 1H and 13C NMR and mass spectroscopy). The spectral details of the synthesized ILs are provided in the supplementary information Figs. S1 to S30.

For molten salt

Molecular Weight:197.97
Hydrogen Bond Acceptor Count:5
Rotatable Bond Count:1
Exact Mass:198.0951412
Monoisotopic Mass:198.0951412
Topological Polar Surface Area:8.8
Heavy Atom Count:13
Complexity:92
Covalently-Bonded Unit Count:2
Compound Is Canonicalized:Yes