Electrostatic field of ions

The second type is typical of interaction between H O and ions. When they meet, water dipoles orient in the electrostatic field of ions, pulled in by the end with the opposite charge and become less mobile. This way form super-molecule associations of the aquatic complex type - [ionCH O) ]. Such process is called hydration, and formed complexes - hydrates. Diluted solutions are dominated by saturated aquatic complexes where each ion is surrounded by water molecules, for instance, Cu[H20]g, Ni[H20]g. Even ions of hydrogen and hydroxyl OH" do not exist in water... 

Redox reactions can be catalyzed by reducible cations substituted into the framework of zeolitic systems as well as polymorphic AIPO4 systems or by cations not located in the framework but in the micropores. In Chapter 8 we will discuss more extensively catalysis by Tia,Si(i 2,)02 systems using peroxides. Here we will initiate the discussion on redox catalysis with Coa Al(i 2.)P04 oxidation catalysts where reducible ions such as Co + substitute for AP+. Catalytic oxidation carried out with oxygen provides an opportunity to discuss radical-type chemistry. A second system that we will discuss is photochemical oxidation induced by the strong electrostatic field of ion-exchanged cations. We will subsequently discuss catalysis by Fe " " and Fe " " ion exchanged zeolites with comparisons to Zn + systems and the important role of the corresponding oxycation. 

The Electrical A nalogue of Magnetic Cooling. Three Processes bg Which Ions Are Introduced into Solution.. 1 Polar Dielectric in an Electrostatic Field. The Concepts of Faraday and Maxwell. The Electrostatic Energy in the Fields of Ions. The. Charging of a Condenser. The Amount of Free Energy Lost, by a Dielectric. The Behavior of Solvents in an Electrostatic Field. A Dielectric in the Field of a Charged Sphere. Two Types of Process Contrasted. 

The same ideas may be applied to the other processes of Fig. 1. The work required to dissociate a diatomic molecule into two electricallt/ neutral atoms may he quite small the dissociation energy of the bromine molecule Br2 in a vacuum, for example, is only 1.915 electron-volts. On the other hand, the work to dissociate a molecule into two atomic ions in a vacuum cannot be as small as this, since work must be done to set up the full electrostatic field of the positive ion, and the full electrostatic field of the negative ion and this must amount to at least a few electron-volts.1 In addition, the non-electrostatic forces may make a small or large contribution. 

The Electrostatic Energy. In Chapter 2 we drew attention to the fact that, when a proton transfer (117) has been carried out in a solvent, the electrostatic fields of two ions have been created and work must have been done to supply the amount of energy associated with these ionic fields. Let us now compare (117) with the process (123), both in aqueous solution at the same temperature. In both cases an (HaO)+ ion will be formed but in (123), when the proton is removed from the (IIS04)-ion, we have to separate the particles against the mutual attraction of the proton and the doubly charged ion (S04)". Consequently, more work must be done against the electrostatic forces of attraction than in the removal of a proton from a neutral particle. 

Let us consider now the work required to remove the first proton and the second proton. When the doubly charged ion of Fig. 46c has been formed, a certain amount of energy has been put into the electrostatic field of the ion this total amount differs, owing to the proximity of the two negative charges, from twice the amount put into the electrostatic... 

In an ionic polymerization the strong electrostatic field of the ion pairs should have a pronounced effect on the ratio of the probabilities of the two placements. Furthermore, solvation of an ion pair is much stronger than of a neutral radical, hence the influence of a solvent on stereospecificity of addition is expected to be much more pronounced in an ionic polymerization than in a radical polymerization. The nature of the gegen ion represents still another factor which is of extreme importance in determining the stereospecificity of the polymerization. 

Gathers and Fuoss have shown that the conductance of poly-(4-vinyl-N-butylpyridinium bromide) increases with the dielectric constant of the medium. The energy of removal of a mobile bromide ion from the electrostatic field of the molecule decreases as the dielectric constant is increased hence the number of free ions and the net charge on the polymeric ion should increase. Both contribute toward increasing the conductance. ... 

When an electrostatic field of field strength E is applied, each type j of ion carrying charge ZjF (per mole) finds itself under the effect of an electric driving force... 

Cation and anion flux across cultured cell monolayers by molecular restricted diffusion within an electrostatic field of force across aqueous pores has been described with a model derived by Adson et al. (1994). The ion fluxes per cross-sectional area of the cell monolayer are defined as... 

When a lanthanide ion is placed in a ligand environment with symmetry lower than spherical, the energies of its partly filled 4f orbitals are split by the electrostatic field of the ligand. The result is a splitting of the 2/ + 1 degeneracy of the free ion states (see Figure 1.2). 

The frequency of the symmetric stretch does not vary with degree of neutralization for hydrated membranes, which was attributed to the shielding of sulfonate anions from the electrostatic field of the Na+ ions. 

One can envision two ground states with parallel electronic spins for the 5f ions in the strong electrostatic field of the Me-0 bonds (28) ... 

The local version of EHCF method was implemented and used for the analysis of the molecular geometries of complexes of iron (II) in works [29, 148,149]. The satisfactory agreement in the description of complexes geometry with different total spins is achieved when the effect of electrostatic field of the metal ion on the ligands is taken into account through the electrostatic polarization of the ligands. Satisfactory estimates of parameters... 

In equation (23), a and a2 are the molecular radii of the reactants and r the internuclear separation between them. For a self-exchange reaction where there is no change in coordination number, ai a2 = a, and if it is assumed that electron transfer occurs between the reactants in close contact, a1 + a2 = r which leads to equation (24). Equations (23) and (24) neglect specific contributions from individual solvent molecules such as hydrogen bonding and, also, possible dielectric saturation effects that may arise because of restricted rotations of solvent dipoles in the near vicinity of the electrostatic fields of the ions. 

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