Big Chemical Encyclopedia

Chemical substances, components, reactions, process design ...

Articles Figures Tables About

Low charge-density ions

Complex Ion Formation. Phosphates form water-soluble complex ions with metallic cations, a phenomenon commonly called sequestration. In contrast to many complexing agents, polyphosphates are nonspecific and form soluble, charged complexes with virtually all metallic cations. Alkali metals are weakly complexed, but alkaline-earth and transition metals form more strongly associated complexes (eg, eq. 16). Quaternary ammonium ions are complexed Htde if at all because of their low charge density. The amount of metal ion that can be sequestered by polyphosphates generally increases... [Pg.339]

To conclude this section let us note that already, with this very simple model, we find a variety of behaviors. There is a clear effect of the asymmetry of the ions. We have obtained a simple description of the role of the major constituents of the phenomena—coulombic interaction, ideal entropy, and specific interaction. In the Lie group invariant (78) Coulombic attraction leads to the term -cr /2. Ideal entropy yields a contribution proportional to the kinetic pressure 2 g +g ) and the specific part yields a contribution which retains the bilinear form a g +a g g + a g. At high charge densities the asymptotic behavior is determined by the opposition of the coulombic and specific non-coulombic contributions. At low charge densities the entropic contribution is important and, in the case of a totally symmetric electrolyte, the effect of the specific non-coulombic interaction is cancelled so that the behavior of the system is determined by coulombic and entropic contributions. [Pg.835]

Ionic liquids are characterised by the following three definition criteria. They consist entirely out of ions, they have melting points below 100 °C and they exhibit no detectable vapour pressure below the temperature of their thermal decomposition. As a consequence of these properties most ions forming ionic liquids display low charge densities resulting in low intermolecular interaction. Figure 7.1 displays some of the most common ions used so far for the formation of ionic liquids. [Pg.183]

The ionic radii discussed above are properly "crystal radii," i.e.. the radii exhibited by (he ions in ionic crystals. Although these radii are probably reasonable representations of the radii of contact of the ions in solution w ith the nearest atoms of solvate molecules, especially for ions of low charge density, nevertheless, most Ions in solution have far larger effective radii because they carry with them a sheath of solvent molecules, die tenacity... [Pg.340]

In contrast, in dipolar aprotic solvents, anion solvation occurs mainly by ion-dipole and ion-induced dipole forces. The latter are important for large, polarizable, soft anions, with low charge density, in soft dipolar aprotic solvents. Therefore, although these solvents tend to be poor anion solvators, they are usually better, the larger and softer the anion. This has the consequence that the reactivity of anions is exceptionally high in dipolar aprotic solvents, and the rate constants of Sn2 reactions can increase by several powers of ten when the solvent is changed from protic to dipolar aprotic cf. Section 5.4.2). [Pg.84]

The complex cation ND4+ has been studied hy X-ray diffraction (49) and by the neutron isotopic difference method (31a), and results show that the coordination is weak, as might be expected for the low charge density. An MD computer simulation study using modified L-J potentials for the ion-water interactions gave good agreement with the ND results (75). [Pg.205]

Electrophiles are akin to acids, while nucleophiles are similar to bases. A centre with a high charge density is called hard, while one with a low charge density is called soft. Nucleophiles with a high charge density, such as hydroxide ions, tend to react more readily with electrophiles with a high charge density, such as protons. Thus, hard nucleophiles tend to react with hard electrophiles. Conversely, soft nucleophiles tend to react with soft electrophiles. [Pg.137]


See other pages where Low charge-density ions is mentioned: [Pg.228]    [Pg.228]    [Pg.464]    [Pg.363]    [Pg.54]    [Pg.316]    [Pg.228]    [Pg.228]    [Pg.464]    [Pg.363]    [Pg.54]    [Pg.316]    [Pg.156]    [Pg.44]    [Pg.594]    [Pg.239]    [Pg.180]    [Pg.101]    [Pg.108]    [Pg.67]    [Pg.411]    [Pg.706]    [Pg.623]    [Pg.95]    [Pg.164]    [Pg.230]    [Pg.282]    [Pg.283]    [Pg.144]    [Pg.72]    [Pg.323]    [Pg.667]    [Pg.729]    [Pg.82]    [Pg.41]    [Pg.168]    [Pg.415]    [Pg.155]    [Pg.264]    [Pg.387]    [Pg.95]    [Pg.667]    [Pg.729]    [Pg.68]    [Pg.133]    [Pg.86]    [Pg.204]    [Pg.207]   
See also in sourсe #XX -- [ Pg.363 ]




SEARCH



Charged ion

Ion density

© 2024 chempedia.info