Ionic liquid
Salts that are liquid at near-ambient temperature are important for electric battery applications, and have been considered as sealants due to their very low vapor pressure.
[11] In 1911 Ray and Rakshit, during preparation of the nitrite salts of ethylamine, dimethylamine, and trimethylamine observed that the reaction between ethylamine hydrochloride and silver nitrate yielded an unstable ethylammonium nitrite (C2H5)NH+3·NO−2 , a heavy yellow liquid which on immersion in a mixture of salt and ice could not be solidified and was probably the first report of room-temperature ionic liquid.
[14] In the 1970s and 1980s, ionic liquids based on alkyl-substituted imidazolium and pyridinium cations, with halide or tetrahalogenoaluminate anions, were developed as potential electrolytes in batteries.
[15][16] For the imidazolium halogenoaluminate salts, their physical properties—such as viscosity, melting point, and acidity—could be adjusted by changing the alkyl substituents and the imidazolium/pyridinium and halide/halogenoaluminate ratios.
In 1992, Wilkes and Zawarotko obtained ionic liquids with 'neutral' weakly coordinating anions such as hexafluorophosphate (PF−6) and tetrafluoroborate (BF−4), allowing a much wider range of applications.
Solubility differences can be exploited in biphasic catalysis, such as hydrogenation and hydrocarbonylation processes, allowing for relatively easy separation of products and/or unreacted substrate(s).
Many classes of chemical reactions, The miscibility of ionic liquids with water or organic solvents varies with side chain lengths on the cation and with choice of anion.
[25] Water is a common impurity in ionic liquids, as it can be absorbed from the atmosphere and influences the transport properties of RTILs, even at relatively low concentrations.
[4] Classically, ILs consist of salts of unsymmetrical, flexible organic cations with symmetrical weakly coordinating anions.
Conventional quaternary ammonium cations also form ILs, e.g. tetraethylammonium (TEA) and tetrabutylammonium (TBA).
Typical anions in ionic liquids include the following: tetrafluoroborate (BF4), hexafluorophosphate (PF6), bis-trifluoromethanesulfonimide (NTf2), trifluoromethanesulfonate (OTf), dicyanamide (N(CN)2), hydrogensulfate (HSO−4), and ethyl sulfate (EtOSO3).
[45] IL 1-butyl-3-methylimidazolium chloride dissolves freeze-dried banana pulp and with an additional 15% dimethyl sulfoxide, lends itself to carbon-13 NMR analysis.
In this way the entire complex of starch, sucrose, glucose, and fructose can be monitored as a function of banana ripening.
[46][47] Beyond cellulose, ILs have also shown potential in the dissolution, extraction, purification, processing and modification of other biopolymers such as chitin/chitosan, starch, alginate, collagen, gelatin, keratin, and fibroin.
[49] Moreover, ILs enable the synthesis of chemically modified starches with high efficiency and degrees of substitution (DS) and the development of various starch-based materials such as thermoplastic starch, composite films, solid polymer electrolytes, nanoparticles and drug carriers.
For buffering during cloudy periods or to enable generation overnight, energy can be stored by heating an intermediate fluid.
This has been achieved using lower temperature extraction processes than current approaches[53] and could help avoid incinerating plastics or dumping them in landfill.
[57][58][59] Some ionic liquids have been shown to reduce friction and wear in basic tribological testing,[60][61][62][63] and their polar nature makes them candidate lubricants for tribotronic applications.
However, the claimed ecological advantage of ionic liquids has been questioned repeatedly and is yet to be demonstrated from a life-cycle perspective.
[64] Ionic liquids' low volatility effectively eliminates a major pathway for environmental release and contamination.
[65][66][67] Ultrasound can degrade solutions of imidazolium-based ionic liquids with hydrogen peroxide and acetic acid to relatively innocuous compounds.
The mixed venoms chemically react with one another to form an ionic liquid, the first naturally occurring IL to be described.
