Water-soluble ionic liquid

Suresh, Lee and coworkers demonstrated oxidation of cyclohexene catalyzed by Mn or Cu complexes using H202 in aqueous phase in a microreador (width = 200 pm and depth = 50 pm) [36], Water-soluble ionic liquid [bmim]BF4 was added (0.5%, v/v) to improve the solubility of cydohexene in the readionbuffer. With the use of a reduced Schiff base-Cu complex, 2-hydroxycyclohexanone was obtained as the maj or produd with 2 5 min residence time, whereas the bulk scale reaction gave 2-cyclohexenol as the major reaction produd. 

Guerrero-Sanchez C, Lobert M, Hoogenboom R et al (2007) Microwave-assisted homogeneous polymerizations in water-soluble ionic liquids an alternative and green approach for polymer synthesis. Macromol Rapid Commun 28 456 64... 

Water-soluble ionic liquids, typically acetate, trifluoroacetate and tetrafluoro-borate salts, can be obtained by the addition of the corresponding silver salt and elimination of the precipitate. This method leads to highly pure ionic liquids containing a very low amount of the chloride anion. However, starting silver salts are expensive, and an equivalent of waste material (AgCl) is generated. 

In parallel, new types of anion have also been described, usually associated with the dialkylimidazolium cation. For example, dicyanamide 18 salts are water-soluble ionic liquids with low viscosity.Other types of anion-containing metals have been reported, such as hexafluoroniobate and tantalate 19 and Co(CO)4 20, but these have found only limited applications." " Ionic liquids formed with... 

New anions have been used to form hydrophilic ionic liquids. The association of the dicyanamide anion with A, N -dialkylpyrrolidinium, tetraalkylammonium and emim 40, (Figure 2.7) leads to water-soluble ionic liquids with melting points below Similar behavior has been observed for phosphate ionic liquids, not only for the corresponding standard [emim]3[P04] (41), but also for polycationic species such as 42. Although they are viscous, these salts are liquid at room temperature. ... 

Adding a polar functional group on the cation will also form water-soluble ionic liquids. Salts 30-33 (Table 2.5), whose imidazolium ring has a hydroxyl functionality, are all soluble in water, even when the hydrophobic hexafluorophosphate anion is used. These salts have been developed for their ability to solubilize inorganic salts (LiCl, HgCl2 and LaCb). ... 

Recently, ionic liquids have been employed as solvents in many catalytic processes, because they provide effective media for reactions involving ionic intermediates. Easy separation of organic products from ionic Uquids is also advantageous. An efficient and rapid method for the oxidation of cydohexene in an ionic liquid medium has been devdoped using a microreactor (length of the channel of the microreactor 3 cm, width 200 pm, depth 50 pm) (Scheme 7.10) [96, 99]. The yield of product is higher than that with conventional batch reactors. The water-soluble ionic liquid 1-butyl-3-methylimidazoUum tetrafluoroborate is used to improve the solubility of cydohexene in the reaction buffer. 

Guerrero Sanchez Carlos, Erdmenger Tina, Sereda Petr, Wouters Daan, and Schubert Ulrich S. Water-soluble ionic liquids as novel stabilizers in suspension polymerization reactions Engineering polymer beads. Chem. Eur. J. 12 no. 35 (2006) 9036-9045. 

When water-miscible ionic liquids are used as solvents, and when the products are partly or totally soluble in these ionic liquids, the addition of polar solvents, such as water, in a separation step after the reaction can make the ionic liquid more hydrophilic and facilitate the separation of the products from the ionic liquid/water mixture (Table 5.3-2, case e). This concept has been developed by Union Carbide for the hydroformylation of higher alkenes catalyzed by Rh-sulfonated phosphine ligand in the N-methylpyrrolidone (NMP)/water system. Thanks to the presence of NMP, the reaction is performed in one homogeneous phase. After the reaction. 

The solubility of CO2 in ionic liquids is strongly dependent on the water content. Saturating [BMIMJPFg with water (it contained up to 2.3 wt% water) reduced the CO2 solubility from 0.54 mol fraction (0.15 wt% water) to only 0.13 mol fraction at 57 bar and 40°C (30). When water is present in excess, CO2 has also been found to induce the separation of water from ionic liquids (55). 

Lin, H. et al.. Solubility of selected dibasic carboxylic acid in water, in ionic liquid of [Bmim][BF4], and in aqueous [BmimHBFJ solutions. Fluid Phase Equilib., 253, 130, 2007. 

Several cleanup methods have been developed for the determination of urea pesticides, involving different basic procedures, such as liquid-liquid partition (30-32,34,36,37), steam distillation (31), and liquid-solid chromatography (9,30,32,34,36,38,56-58). Different factors, e.g., water solubility, ionic and polarity properties, thermal stability, and the molecular weight of the compounds, determine the choice of the cleanup method. Moreover, micro-cleanup procedures and online enrichment techniques have been introduced for the automated determination of phenylureas (60). Table 6 summarizes the use of the different cleanup procedures in the determination of urea pesticides. 

For the electrodeposition of metals or alloys from air- and water-stable ionic liquids, it is necessary first to dissolve the corresponding metal ions in the ionic liquid. Such a dissolution process is made possible by introducing excess amounts of halide ions (such as Cl ) to form soluble metal-halide complex anions. Alternatively, the metal is dectrochemically oxidized in the ionic liquid to form the soluble salt such as Sn(Tf2N) in the trimethyl-n-hexylammonium [bis(trifluoromethyl)sulfonyl]amide ([TMHAj TfiN ) ionic liquid. 

As with all catalytic reactions, recent advances in oxidation chemistry have been used in developing systems that use environmentally benign water or ionic liquids " " as solvents. The economical, soluble and easily prepared complex Cu(acac)2 (43) is an active and selective catalyst for the oxidation of secondary alcohols in ionic liquids at room temperature" . Further discussion of these reactions can be found in several excellent reviews """. ... 

Highly soluble cationic ruthenium-dusters complexes have also been used for hydrogenation of aromatic substrates [31]. Compared with water these ionic liquids dissolve higher concentration of hydrogen gas which leads to increased reaction rate in biphasic conditions. 

Oxidoreductases are of special interest for the enantioselective reduction of prochiral ketones [49]. Formate dehydrogenase from Candida boidinii was found to be stable and active in mixtures of [MMIM][MeS04] with buffer. The apphcation of alcohol dehydrogenases for enzyme-catalyzed reactions in the presence of water-miscible ionic liquids could make use of another advantage of these solvents they increase the solubility of hydrophobic compounds in aqueous systems. By addition... 

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