Ionic liquids acid-base property

The Lewis acid-base properties of these ionic liquids are determined by the chloroaluminate species. The equilibrium of the chloroaluminate liquid is primarily described by two equilibria at x AICI3 below 0.67 ... 

Another type of the facilitated transfer is that involving molecules with acid-base properties. A construction of ion partition diagram of the solute, which is analogous to Pourbaix s -> potential-pH diagrams widely used in electrochemistry of corrosion, has been proposed as a convenient tool that makes it possible to relate the voltammetric behavior to the partition of the neutral and the ionic species, as well as to acid-base equilibria in the adjacent liquid phases [xi]. 

The relative basicity of anions in ionic liquids is directly related to the question of their acid-base properties which cannot be determined by pH measurements due to the non-aqueous nature of these media. However, MacFarlane and Forsyth argue that an acid dissolved in an ionic liquid based on anions which are typically more basic than water, such as acetate, must be more dissociated than when dissolved in water [122],... 

Most ions constituting ionic liquids can be categorized according to their Lewis acid/base properties (i.e., their capability to accept or to donate an electron pair) nevertheless, some ions may be considered according to the Bronsted definition, i.e., on the basis of their ability to accept or donate a proton. Typical ionic liquids are those based on neutral or very weakly basic anions (BF4, PF, NOf, CHsSO, 4 f2N ) and neutral (tetraalkylammonium, dialkyl-pyrrolidium, trialkylsulfonium) or weakly acidic cations (1,3-dialkylimidazolium and 1,2,3-trialkylimidazolium) (Figure 4.1). 

Ishiguro, S.-L, Umebayashi, Y, Kanzaki, R. and Fujii, K., Structure, solvation, and acid-base property in ionic liquids. Pure J pl. Chem. 82,1927-1941 (2010). 

Metal oxides are ionic solids, non-metal oxides are simple molecular covalent gases and liquids. The variation of acid-base properties of the oxides in aqueous solution is strongly correlated with the position of the metal-non-metal line in the periodic table. 

Kanzaki R, Doi H, Song X et al (2012) Acid-base property of N-methylimidazoliimi-based protic ionic liquids depending on anion. J Phys Chem B 116 14146-14152... 

Lipophilicity of a molecule is measured by its distribution behavior in a biphasic system either liquid-liquid (partition coefficient in 1-octanol-water) or solid-liquid (retention in RP-TLC or RP-HPLC) systems. According to definition suggested by lUPAC lipophilicity expresses the affinity of a molecule for a lipophilic environment. A reference scale representing lipophilicity appears to be the solute distribution between octanol and water. Berthod Carda-Broch (Berthod Carda-Broch) proposed another lipophilicity scale measuring ionic liquid BMIM PFg-water distribution constants. Relationship between the obtained values and respective octanol-water coefficients for a series of aromatic compounds differing in acid-base properties revealed that only the neutral compounds or ionizable ones with zwitterionic properties showed similar distribution behavior in the... 

Song X, Kanzaki R, Ishiguro S-I, Umebayashi Y (2012) Physicochemical and acid-base properties of a series of 2-hydroxyethylammonium-based protic ionic liquids. Anal Sci... 

Thus, most ionic liquids are formed from cations that do not contain acidic protons. A summary of the applications and properties of ionic liquids may be found in a number of recent review articles [3]. The most common classes of cations are illustrated in Figure 2.1-1, although low melting point salts based on other cations, such as complex poly cationic amines [4] and heterocycle-containing drugs [5], have also been prepared. 

Moreover, these experiments reveal some unique properties of the chlorostan-nate ionic liquids. In contrast to other known ionic liquids, the chlorostannate system combine a certain Lewis acidity with high compatibility to functional groups. The first resulted, in the hydroformylation of 1-octene, in the activation of (PPli3)2PtCl2 by a Lewis acid-base reaction with the acidic ionic liquid medium. The high compatibility to functional groups was demonstrated by the catalytic reaction in the presence of CO and hydroformylation products. 

The types of ionic liquids shown in Figure 5.4 have been most extensively studied, especially ones based on chloroaluminate. Whilst these chloroaluminate materials also display useful Lewis acid properties they are highly air and moisture sensitive, which renders them relatively commercially unattractive. Newer ionic liquids containing C104 and NOa anions, for example, which are less air and moisture sensitive, are now being more widely studied, but these are less catalytically active. Other than lack of vapour pressure and catalytic properties there are several other features common to most ionic liquids that make them attractive reaction solvents. These include ... 

The anions, on the other hand, determine to a large extent the chemical properties of the system. For example, the main anions present in chloroaluminate ionic liquid systems such as (emim)Cl-AlCl3 are CT, which is a Lewis base (AICI4) , which is neither acidic nor basic and the Lewis acid (AbCb). The concentration of each anion, and therefore the Lewis acidity of the system, varies depending on the relative amounts of AICI3 and (emim)Cl added to the system. 

The ability to vary the composition of Lewis or Bronsted acid adds an additional dimension to the tuneability of the eutectic-based ionic liquids. It has been shown that the Lewis acidity of the liquid affects not only the physical properties of the liquids but also the electrochemical behavior. Type I ionic liquids are also clearly... 

The electrodeposition of chromium in a mixture of choline chloride and chromium(III) chloride hexahydrate has been reported recently [39]. A dark green, viscous liquid is obtained by mixing choline chloride with chromium(III) chloride hexahydrate and the physical properties of this deep eutectic solvent are characteristic of an ionic liquid. The eutectic composition is found to be 1 2 choline chloride/chromium chloride. From this ionic liquid chromium can be electrode-posited efficiently to yield a crack-free deposit [39]. Addition of LiCl to the choline chloride-CrCl3-6H20 liquid was found to allow the deposition of nanocrystalline black chromium films [40], The use of this ionic liquid might offer an environmentally friendly process for electrodeposition of chromium instead of the current chromic acid-based baths. However, some efforts are still necessary to get shining... 

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