The effect of anions

Finally, the vanadyl complex was tested in the trimethylsilylcyanation of aldehydes (Scheme 5) [17] and a significant effect of the anion in the solvent... 

Similar conclusions concerning the effect of the anion and impurities in the ionic liquid on the cyclopropanation reaction have been drawn in a recently published study [47]. Ionic liquids with the formula [bmim][X], where X = OTf, NTf2, PFe, and BF4, were used. The catalyst used in this study was 6b-Cu(OTf). In all cases, good enantioselectivities (89-97% ee) were obtained and these are similar to those obtained in chloroform. The influence of the presence of halogen anions was tested by the addition of 5% [bmim] [Cl] or [bmim][Br] to [bmim][BF4]. In both cases, a catalytically inactive solution was obtained, showing the detrimental effect of these anions on the reaction. 

The effects of the anions (i.e., their specific adsorbabilities) increase in the order F < Cr < Br < I . This trend is due to the fact that the solvation energy decreases with increasing crystal radius as one goes from F to I , and the transfer of the ions to the inner Helmholtz plane is facilitated accordingly. The opposite picture is seen for surface-active cations (e.g., [N(C4H5)4]+) the descending branch of the ECC is depressed, and the PZC shifts in the positive direction. 

The hydrolysis of the zinc ion in varying anionic media has been investigated. In the pH range of 2.0 to 6.0 a dependence on the anion present is observed, with either sodium nitrate, sodium perchlorate, or sodium chloride at 0.5 M concentration. Only monomeric species were observed and [Zn(OH)]+(aq) was found in all three solutions while Zn(OH)2(aq) was only found in the perchlorate solution, demonstrating the effect of the anionic medium on the formation and stability of the hydrolytic species.339 ... 

The above results concerning the fractal dimension as functions of the solution temperature, the CPE exponent, and the depression parameter are demonstrated again in their other investigation of the effect of the anion addition on pit morphology of Inconel alloy 600 at elevated temperatures.54... 

The effect of the anion and of the ligand deserves a separate consideration. 

Table 4.2 Effect of the anion on the melting point of the 1 -butyl-3-methylimidazolium, [bmim]+, cation...

The increase in the anion concentration results in higher values of Cj at the maximum and in the shift of the maximum toward the zero charge density. The shift of the peak with increasing concentration is caused by the screening effect of the anions, accumulated in the diffuse layer and linked to the positive ends of the solvent dipoles. However, the changes in the shape of the C, vs. plots are greater on the negative than on the... 

The effect of acetate, citrate, and thiourea on Pb underpotential deposition on Ag(lll) has been studied. The effects of the anionic character of the additives were discussed in relation to changes in voltammograms. The two-dimensional phase transformation was also discussed. The influence of various additives such as dimethylfluoride (DMF) and pyridine on cyclic voltammograms of Cu underpotential deposition on Pt(lll) was observed. Cu underpotential deposition on Pt(lll) was studied in the presence of crystal violet, coumarin, and hydroquinone. ... 

Bechgaard K (1982) TMTSF2X salts. Preparation, stmcture and effect of the anions. Mol Cryst Liq Cryst 79 1-13... 

Domariska, U. and Mazurowska, L., Solubility of 1,3-dialkylimidazolium chloride or hexafluorophosphate or methylsulfonate in organic solvents. Effect of the anions on solubility. Fluid Phase Equilib., 221, 73, 2004. 

Headley, A. D. and Jackson, N. M., The effect of the anion on the chemical shifts of the aromatic hydrogen atoms of liquid l-butyl-3-methylimidazolium salts, /. Phys. Org. Chem., 15, 52, 2002. 

Though the five-coordinate complexes, except for p-oxo dimers, coordinate sixth ligands, the association constants are low (K < 103 M-1) because of the strong trans effect of the anionic ligand (equation 13).18 In the presence of excess ligand, the anionic ligand may be displaced (equation 14).13... 

The effect of the anion on the copolymerization rate is controversial. Hilt et al.41 established for different sodium halides the following order of efficiency F < Cl < Br < J . This order was interpreted on the basis of the increase in nucleophilicity or polarizability of the anions. Sfluparek and Mleziva 43) observed that the reaction rate of the benzoate anion was about twice as high as that of the bromide anion in the copolymerization of epichlorohydrine with phthalic anhydride. On the other hand, Luston and Manasek56) did not detect any effect of the anion size on the copolymerization rate initiated by tetramethylammonium and tetrabutylammonium halides. 

The formation of the complex creates a very strong electron-withdrawing group which helps the withdrawal of the electrons from the carbon-carbon bond which is breaking. Catalysis results because this electron-withdrawing effect is much stronger than the effect of the anion in the uncatalysed decarboxylations. 

The results for effects upon mechanical stability are summarised in Table II. That lithium laurate behaves similarly to, say, potassium laurate is perhaps surprising, in that it is known that a lithium salt is mor ffective in reducing the mechanical stability of natural rubber -ftian is the corresponding potassium salt (6.). The inference has been drawn that the counterion of the car-boxylate soap has a negligible effect upon the ability of the soap to enhance mechanical stability, relative to the effect of the anion, at least for those cations for which specific adsorption effects are absent. 

COl" > N03 > eland that the stabilities of the catalysts during reaction in a CO + 3H2 mixture at 500 °C fell in the same order. It was concluded that the main effects of the anions were manifested during the calcination of the coprecipitates. It was also observed that the hydrothermally aged materials gave reduced samples with very similar methanation activities to those derived from the freshly prepared materials. 

Garcia MT, Gathergood N, Scammells PJ (2005) Biodegradable ionic liquids Part II. Effect of the anion and toxicology. Green Chem 7(1) 9-14... 

The choice of anion will have a known effect on the physicochemical properties of the ionic liquid. To demonstrate the anion effect, selected data on properties of general interest to electrochemists (density, viscosity, conductivity and electrochemical window) have been gathered in Table 2.2. In each case, the anion is paired with the same cation l-ethyl-3-methylimidazolium. Certain trends from this data can be generalized, as well as in other collections of such data (for example, see Ref. [61] and references therein), that hold true regardless of the identity of the cation. For example, the effect of the anion on density follows the trend ... 

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