Solvation, ion

A gas phase ionic cluster can be described as a core ion solvated by one or more neutral atoms or molecules... 

This fomuila does not include the charge-dipole interaction between reactants A and B. The correlation between measured rate constants in different solvents and their dielectric parameters in general is of a similar quality as illustrated for neutral reactants. This is not, however, due to the approximate nature of the Bom model itself which, in spite of its simplicity, leads to remarkably accurate values of ion solvation energies, if the ionic radii can be reliably estimated [15],... 

Meot-Ner M 1984 Ionic hydrogen bond and ion solvation 2. Solvation of onium ions by 1-7 water molecules. Relations between monomolecular, specific and bulk hydration J. Am. Chem. Soc. 106 1265-72... 

Dang L X, J E Rice, J Caldwell and P A Kollman 1991. Ion Solvation in Polarisable Water Molecular Dynamics Simulations. Journal of the American Chemical Society 113 2481-2486. 

Many organic reactions involve acid concentrations considerably higher than can be accurately measured on the pH scale, which applies to relatively dilute aqueous solutions. It is not difficult to prepare solutions in which the formal proton concentration is 10 M or more, but these formal concentrations are not a suitable measure of the activity of protons in such solutions. For this reason, it has been necessaiy to develop acidity functions to measure the proton-donating strength of concentrated acidic solutions. The activity of the hydrogen ion (solvated proton) can be related to the extent of protonation of a series of bases by the equilibrium expression for the protonation reaction. 

The main problem in the study of the role of these parameters in electrolyte conductivity is their interdependence. A change in composition of a binary solvent changes viscosity, along with the permittivity, ion-ion association, and ion solvation, which may be preferential for one of the two solvents and therefore also changes the Stokes radii of the ions. 

A further important feature of HMPA is its stabilizing effect on the Redox potential of [Fe(CO)4]2 by ion solvation. In less polar solvents, electron-transfer reactions take place and [Fe(CO)4]2 is oxidized to [HFe3(CO)iThis redox reaction is suppressed in HMPA. 

Species 3.6 is therefore indeed a complex which, in classical terms, may be called a nitrosyl ion solvated with one molecule of water. The complex is calculated to be more stable than its fragments by 75 kJ mol-1. It is likely, as the authors say, that this calculated value is a little smaller than the true value. 

It should be noted that protonated acetyl nitrate can be regarded as a nitronium ion solvated by acetic acid74 (I)... 

The frequency-dependent spectroscopic capabilities of SPFM are ideally suited for studies of ion solvation and mobility on surfaces. This is because the characteristic time of processes involving ionic motion in liquids ranges from seconds (or more) to fractions of a millisecond. Ions at the surface of materials are natural nucleation sites for adsorbed water. Solvation increases ionic mobility, and this is reflected in their response to the electric field around the tip of the SPFM. The schematic drawing in Figure 29 illustrates the situation in which positive ions accumulate under a negatively biased tip. If the polarity is reversed, the positive ions will diffuse away while negative ions will accumulate under the tip. Mass transport of ions takes place over distances of a few tip radii or a few times the tip-surface distance. 

The real energy of ion solvation, af, defined by Eq. (2), expresses the change in ion energy upon its transfer from a gas phase into a solution. Unlike the chemical energy of solvation, psi, the value of the real energy of solvation, also in the standard state, can be calculated from experimental data using the formula, e.g., for the hydration of the cation ... 

The reliability of the experimental A / MX) values was checked for systems containing nitrobenzene, nitromethane, and 1,2-dichlo-roethane as organic solvent by comparing the differences in these values for various pairs of salts with the differences in the Galvani (i.e.,distribution) potemtials, A cp MX) for the same pairs. The differences should be the same. The A cp or Afip data can be used to estimate ion solvation energies in a water-saturated solvent. ... 

At present, intercalation compounds are used widely in various electrochemical devices (batteries, fuel cells, electrochromic devices, etc.). At the same time, many fundamental problems in this field do not yet have an explanation (e.g., the influence of ion solvation, the influence of defects in the host structure and/or in the host stoichiometry on the kinetic and thermodynamic properties of intercalation compounds). Optimization of the host stoichiometry of high-voltage intercalation compounds into oxide host materials is of prime importance for their practical application. Intercalation processes into organic polymer host materials are discussed in Chapter 26. 

Apart from the study of physicochemical aspects such as ion solvation, and bio-mimetic aspects such as photosynthesis or carrier-mediated ion transfer (Volkov et al., 1996, 1998), there are several areas of potential applications of electrochemical IBTILE measurements comprising electroanalysis, lipophilicity assessment of drugs, phase transfer catalysis, electro-assisted extraction, and electrocatalysis. 

Clearly, then, the chemical and physical properties of liquid interfaces represent a significant interdisciplinary research area for a broad range of investigators, such as those who have contributed to this book. The chapters are organized into three parts. The first deals with the chemical and physical structure of oil-water interfaces and membrane surfaces. Eighteen chapters present discussion of interfacial potentials, ion solvation, electrostatic instabilities in double layers, theory of adsorption, nonlinear optics, interfacial kinetics, microstructure effects, ultramicroelectrode techniques, catalysis, and extraction. 

Much attention has been directed since olden times towards ion solvation, which is a key concept for understanding various chemical processes with electrolyte solutions. In 1920, a theoretical equation of ion solvation energy (AG ) was first proposed by Born [1], who considered the ion as a hard sphere of a given radius (r) immersed in a continuous medium of constant permittivity (e), and then defined AG as the electrostatic energy for charging the ion up to ze (z, the charge number of the ion e, the elementary charge) ... 

The purpose of this chapter is to discuss mainly recent development in the theory of ion solvation energy. Because we allowed much space for introducing our new, non-... 

Bornian theory of the Gibbs free energy of ion resolvation, a vast amount of work dealing with ion solvation and resolvation could not fully be reviewed. The reader is referred to some books [2-5] and review articles [6-10] for a general survey. 

The modification by method 2 is more acceptable. Although several types of modifications have been reported, Abraham and Liszi [15] proposed one of the simplest and well-known modifications. Figure 2(b) shows the proposed one-layer model. In this model, an ion of radius r and charge ze is surrounded by a local solvent layer of thickness b — r) and dielectric constant ej, immersed in the bulk solvent of dielectric constant ),. The thickness (b — r) of the solvent layer is taken as the solvent radius, and its dielectric constant ej is supposed to become considerably lower than that of the bulk solvent owing to dielectric saturation. The electrostatic term of the ion solvation energy is then given by... 

On the assumption that = 2, the theoretical values of the ion solvation energy were shown to agree well with the experimental values for univalent cations and anions in various solvents (e.g., 1,1- and 1,2-dichloroethane, tetrahydrofuran, 1,2-dimethoxyethane, ammonia, acetone, acetonitrile, nitromethane, 1-propanol, ethanol, methanol, and water). Abraham et al. [16,17] proposed an extended model in which the local solvent layer was further divided into two layers of different dielectric constants. The nonlocal electrostatic theory [9,11,12] was also presented, in which the permittivity of a medium was assumed to change continuously with the electric field around an ion. Combined with the above-mentioned Uhlig formula, it was successfully employed to elucidate the ion transfer energy at the nitrobenzene-water and 1,2-dichloroethane-water interfaces. 

When the ion is much larger than the solvent, it can be assumed that the number (N) of solvent molecules adjacent to the ion is proportional to the surface area of the ion N = An p (where p is the number of solvent molecules per unit surface area of the ion). Accordingly, the contribution of the CT interaction to the ion solvation energy AG is given by... 

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