4086-73-1Relevant articles and documents
Anion Analysis of Ionic Liquids and Ionic Liquid Purity Assessment by Ion Chromatography
Rutz, Christina,Schmolke, Laura,Gvilava, Vasily,Janiak, Christoph
supporting information, p. 130 - 135 (2017/02/05)
The simultaneous determination of halide impurities (fluoride, chloride, bromide, and iodide) and ionic liquid (IL) anions (tetrafluoroborate, hexafluorophosphate, and triflimide) using ion chromatography was developed with a basic, non-gradient ion chromatography system. The non-gradient method uses the eluent Na2CO3/NaHCO3in water/acetonitrile (70:30 v:v) on the AS 22 column to enable a rapid and simultaneous analysis of different IL and halide anions within an acceptable run-time (22 min) and with good resolution R of larger than 2.4, a capacity k′ between 0.4 and 5.1, selectivities α between 1.3 and 2.1, and peak asymmetries Asof less than 1.5. Halide impurities below 1 ppm (1 mg·L–1of prepared sample solution) could be quantified. A range of ionic liquids with tetrafluoroborate [BF4]–, hexafluorophosphate [PF6]–, and bis(trifluoromethylsulfonyl)imide (triflimide) [NTf2]–anions combined with cations based on imidazole, pyridine, and tetrahydrothiophene could be analyzed for their anion purity. The IL-cations do not influence the chromatographic results. With the analysis of 18 ILs differing in their cation-anion combination we could prove the general applicability of the described method for the anion purity analysis of ionic liquids with respect to halide ions. The IL-anion purity of most ILs was above 98 wt %. The highest IL-anion purity was 99.8 wt %, implying anion impurities of only 0.2 wt %. The used halide anion from the synthesis route was the major anion impurity, yet with chloride also bromide and fluoride (potentially from hydrolysis of [BF4]–) were often detected. When iodide was used, at least chloride but sometimes also bromide and fluoride was present. However, even if the IL-anion content is above 99 wt %, it does not necessarily indicate an ionic liquid devoid of other impurities. From the IC analysis, one can also deduce a possible cation impurity if one takes into account the expected (calculated) IL-anion content. A matching experimental and theoretical IL-anion content excludes, a higher experimental content indicates the presence of residual KBF4, NH4PF6, or LiNTf2salt from the halide to IL-anion exchange.
Does alkyl chain length really matter? Structure-property relationships in thermochemistry of ionic liquids
Verevkin, Sergey P.,Zaitsau, Dzmitry H.,Emel'Yanenko, Vladimir N.,Ralys, Ricardas V.,Yermalayeu, Andrei V.,Schick, Christoph
, p. 84 - 95 (2013/07/28)
DSC was used for determination of reaction enthalpies of synthesis of ionic liquids [Cnmim][Cl]. A combination of DSC with quantum chemical calculations presents an indirect way to study thermodynamics of ionic liquids. The indirect procedure for vaporization enthalpy was validated with the direct experimental measurements by using thermogravimetry. First-principles calculations of the enthalpy of formation in the gaseous phase have been performed for the ionic species using the CBS-QB3 and G3 (MP2) theory. Experimental DSC data for homologous series of alkyl substituted imidazolium, pyridinium, and pyrrolidinium based ionic liquids with anions [Cl] and [Br] were collected from the literature. We have shown that enthalpies of formation, enthalpies of vaporization, and lattice potential energies are linearly dependant on the alkyl chain length. The thermochemical properties of ILs generally obey the group additivity rules and the values of the additivity parameters for enthalpies of formation and vaporization seem to be very close to those for molecular compounds.
Preparation of second generation ionic liquids by efficient solvent-free alkylation of N-heterocycles with chloroalkanes
Cravotto, Giancarlo,Gaudino, Emanuela Calcio,Boffa, Luisa,Leveque, Jean-Marc,Estager, Julien,Bonrath, Werner
, p. 149 - 156 (2008/09/17)
Non-conventional techniques, such as microwave (MW) and power ultrasound (US) as well as combined MW/US irradiation, have been used to promote one-pot synthesis of second-generation ionic liquids (ILs), cutting down reaction times and improving yields. However, the use of chloroalkanes in the alkylation of N-heterocycles requires more drastic conditions if results are to match those obtained with more reactive alkyl halides. The present paper describes a series of MW- or MW/US-promoted IL preparations starting from chloroalkanes and classic heterocycles (1-methylimidazole, pyridine and 1-methylpyrrolidine). When reactions were carried out under conventional heating in an oil bath they required longer reaction times and gave poorer yields. 1H-NMR analysis and ion-exchange chromatography showed that the present solventless procedure afforded ILs of satisfactory purity. The observed high yields (usually 70-98% isolated), and short reaction times showed that a straightforward access to ILs can be also achieved with the use of alkyl chlorides, resulting in a considerable reduction of costs.