3-Methylpiperidinium ionic liquids

[EN] A wide range of room temperature ionic liquids based on the 3-methylpiperdinium cation core were produced from 3-methylpiperidine, which is a derivative of DYTEKs (R) A amine. First, reaction with 1-bromoalkanes or 1-bromoalkoxyalkanes generated the corresponding tertiary amines (Rm beta pip, R = alkyl or alkoxyalkyl); further quaternisation reactions with the appropriate methylating agents yielded the quaternary [Rmm(beta)pip]X salts (X-= I-, [CF3CO2]-or [OTf](-); Tf = -SO2CF3), and [Rmm(beta)pip][NTf2] were prepared by anion metathesis from the corresponding iodides. All [NTf2]-salts are liquids at room temperature. [Rmm(beta)pip]X (X-= I-, [CF3CO2]-or [OTf](-)) are low-melting solids when R = alkyl, but room temperature liquids upon introduction of ether functionalities on R. Neither of the 3-methylpiperdinium ionic liquids showed any signs of crystallisation, even well below 0 degrees C. Some related non-C-substituted piperidinium and pyrrolidinium analogues were prepared and studied for comparison. Crystal structures of 1-hexyl-1,3-dimethylpiperidinium tetraphenylborate, 1-butyl-3-methylpiperidinium bromide, 1-(2-methoxyethyl)1- methylpiperidinium chloride and 1-(2-methoxyethyl)-1-methylpyrrolidinium bromide are reported. Extensive structural and physical data are collected and compared to literature data, with special emphasis on the systematic study of the cation ring size and/or asymmetry effects on density, viscosity and ionic conductivity, allowing general trends to be outlined. Cyclic voltammetry shows that 3-methylpiperidinium ionic liquids, similarly to azepanium, piperidinium or pyrrolidinium counterparts, are extremely electrochemically stable; the portfolio of useful alternatives for safe and high-performing electrolytes is thus greatly extended.We would like to acknowledge the EPSRC NCS in Southampton for the single crystal X-ray diffraction data collection and INVISTA Intermediates for funding.Belhocine, T.; Forsyth, SA.; Gunaratne, HQN.; Nieuwenhuyzen, M.; Nockemann, P.; Vaca Puga, A.; Seddon, KR.... (2015). 3-Methylpiperidinium ionic liquids. Physical Chemistry Chemical Physics. 17(16):10398-10416. doi:10.1039/C4CP05936KS10398104161716C. Mikolajczak , M.Kahn, K.White and R. T.Long, Lithium-ion Batteries Hazard and Use Assessment, Springer, New York, 2012Choi, N.-S., Chen, Z., Freunberger, S. A., Ji, X., Sun, Y.-K., Amine, K., … Bruce, P. G. (2012). Challenges Facing Lithium Batteries and Electrical Double-Layer Capacitors. 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Azepanium ionic liquids

The seven-member alicyclic secondary amine, azepane, has been used as starting material to synthesise a new family of room temperature ionic liquids. Such useful transformations of this coproduct of diamine production processes, generated in large amounts in the polyamide industry, would mitigate its disposal, which usually involves combustion. Reaction of azepane with 1-bromoalkanes or 1-bromoalkoxyalkanes produced the corresponding tertiary amines with good selectivity; further quaternisation reactions with the appropriate methylating agents yielded quaternary azepanium salts, [Rmazp]X (R = alkyl or alkoxyalkyl; X- = I - , [CF3 CO2 ] - or [OTf]- ; Tf = (tri¿uoromethyl)sulfonyl). Analogous [NTf2 ] - salts have also been produced by metathetic reactions. Liquid temperature ranges are signi¿cantly affected by the nature of the anion and the substituents on the azepanium cation core; for example, [CF3 CO2 ] - or [OTf]- salts based on cations with alkyl substitution are solids, whereas those with alkoxyalkyl substitution are liquids at ambient temperature. The crystal structures of [C4 mazp][CF3 CO2 ], [C4 mazp]I and [C6 mazp][NTf2 ] (C4 = butyl, C6 = hexyl) are reported. The effects of the structural features of cations and anions on density, viscosity and conductivity data are discussed. The presence of ether linkages in the cationic side chains causes a marked decrease in viscosities and an increase in conductivities. Cyclic voltammetry showed that azepanium ionic liquids exhibit extremely wide electrochemical windows, thus becoming promising and safe alternatives to electrolytes based on volatile organic compoundsBelhocine, T.; Forsyth, SA.; Gunaratne, HQN.; Nieuwenhuyzen, M.; Nockemann, P.; Vaca Puga, A.; Seddon, KR.... (2011). Azepanium ionic liquids. Green Chemistry. 13(11):3137-3155. doi:10.1039/c1gc15189dS31373155131

New ionic liquids from azepane and 3-methylpiperidine exhibiting wide

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