Degree of solvation

Certainly these approaches represent a progress in our understanding of the interfacial properties. All the phenomena taken into account, e.g., the coupling with the metal side, the degree of solvation of ions, etc., play a role in the interfacial structure. However, it appears that the theoretical predictions are very sensitive to the details of the interaction potentials between the various species present at the interface and also to the approximations used in the statistical treatment of the model. In what follows we focus on a small number of basic phenomena which, probably, determine the interfacial properties, and we try to use very transparent approximations to estimate the role of these phenomena. 

The reactivity of a nucleophilic reagent may also depend on stereochemical conformation, degree of solvation and hydrogen-bonding,... 

As pointed out by Chapman et the steric requirements of the reagents and the degree of solvation of the substrate at the reacting center should also be considered when comparing the nucleophilicities of different amines toward different substrates. The large number of factors which may be involved clearly call for much more work in this area. 

This rale follows immediately from Stokes s law for the motion of spherical bodies in viscous fluids when assuming constant radii. It is applicable in particular for the change in ionic mobility that occurs in a particular solvent when the temperature is varied. Between solvents it remains valid when the electrolytes have poorly solvated ions, such as N(C2H5)4l. For other electrolytes we find rather significant departures from this rale. These are due in particular to the different degrees of solvation found for the ions in different solvents, and hence their different effective radii. 

C -CP-MAS NMR provides subtle information about the degree of solvation of the polymer chains of a CFP in a given solvent and consequently it may be qualitatively correlated with the nanometer scale morphology of the polymer matrix. In fact, the prerequisite that enables a polymer framework to develop a nanoporosity is the ability of the polymer chains and its pendants to be suitably solvated by the liquid medium [26-28]. Therefore, C -CP-MAS NMR spectra provide the basis for a first level screening of the possibility of a CFP in a given solvent to be employed as an hexo-template, able to accommodate metal nanoclusters chemically produced in its interior (see below and Ref. [29]). 

Further, in the case of virtually non-existent ion-solvent interactions (low degree of solvation), so that solute-solute interactions become more important, Kraus and co-workers47 confirmed that in dilute solutions ion pairs and some simple ions occurred, in more concentrated solutions triple ions of type M+ X M+ orX M+X andinhighly concentrated solutions even quadrupoles the expression triple ions was reserved by Fuoss and Kraus48 for non-hydrogen-bonded ion aggregates formed by electrostatic attraction. 

In the meantime, it should not be forgotten that all the equations involving the proton have been written in a conventional, i.e., the most concise, way as the degree of solvation of the proton in a solvent such as HOAc is unknown (cf., reaction 4.53). 

Another variable that influences the saturation solubility of a drug molecule is its degree of solvation. Since the anhydrous, hydrated, and alcoholated forms of a drug have slightly different solubilities, they may well have different dissolution rates and, therefore, different rates of absorption. However, these differences may not be clinically significant [35],... 

The viscosity of colloidal dispersions is affected by the shape of the dispersed phases. Sphero-colloids form dispersions of relatively low viscosity, while systems containing linear particles are generally more viscous. The relationship of particle shape and viscosity reflects the degree of solvation of the particles. In... 

The H2S+ ion is generally termed a lyonium ion and the S" ion is termed a lyate ion. The symbol H2S+ (for example H30+, CH3COOH2+, etc.) refers only to a proton solvated by a suitable solvent and does not express either the degree of solvation (solvation number) or the structure. For example, two water molecules form the lyonium ion H30+, termed the oxonium (formerly hydronium or hydroxonium) ion, and the lyate ion OH", termed the hydroxide ion. 

It follows from Eqs. (2.6.6), (2.6.8) and (2.6.10) that the presence of the solvent has two effects on the ionic mobility the effect of changing viscosity and that of changing the ionic radius as a result of various degrees of solvation of the diffusing particles. If the effective ionic radius does not change in a number of solutions with various viscosities and if ion association does not occur, then the Walden rule is valid for these solutions ... 

Figure 20. (a) Mass spectrum showing the reaction of Mg+ with D2O. (b) Energy required to form MgOH+ as a function of degree of solvation. Taken with permission from ref. 135. 

The above peptide results established general patterns that are apparent in protein spectra. However, most proteins differ from small peptides in terms of the degree of solvation and the uniformity of secondary structure segments. Although a peptide helix may terminate in a large... 

The small size of the proton relative to its charge makes the proton very effective in polarizing the molecules in its immediate vicinity and consequently leads to a very high degree of solvation in a polar solvent. In aqueous solutions, the primary solvation process involves the formation of a covalent bond with the oxygen atom of a water molecule to form a hydronium ion H30 +. Secondary solvation of this species then occurs by additional water molecules. Whenever we use the term hydrogen ion in the future, we are referring to the HsO + species. 

A more subtle chemical influence is the variation of the anion associated with a cationic spin crossover system, or of the nature and degree of solvation of salts or neutral species. These variations can result in the displacement of the transition temperature, even to the extent that SCO is no longer observed, or may also cause a fundamental change in the nature of the transition, for example from abrupt to gradual. The influence of the anion was first noted for salts of [Co(trpy)2]2+ [142] and later for iron(II) in salts of [Fe(paptH)2]2+ [143] and of [Fe(pic)3]2+ [127]. For the [Fe(pic)3]2+ salts the degree of completion and steepness of the ST curve increases in the order io-dide[Pg.41]

T. K. Reiser, A. Macromolecules, in press.). The concentration dependence comes form the "opening" up of the secondary structure of the phenolic resin as the progressive formation of phenolate Ions leads to higher degree of solvation and more facile diffusion paths. 

The degree of solvation of the reactants and activated complex affect the rate of reaction. When the activated complex is solvated to a greater extent in comparison to reactants, the rate of reaction will be greater than that in a non solvating solvent. This is because the activity coefficient of the complex is smaller than it is in a solvent that does not solvate it. This lowers the potential energy of activated complex or causes a decrease in the activation energy of the reaction. 

The redox potential of an electron transfer process involving a metal complex is influenced by various factors typically, in addition to the many times cited inductive effects of the ligands (together with the eventual substituents of the ligands themselves) and the stereochemistry of the redox couples, the degree of solvation of the complex and the temperature also play an important role. In an attempt to rationalize the effects of these factors on the redox potential, as well as the relationship between the redox potential and the spectroscopic properties of the complex, linear correlations between redox potential and widely differing chemical and physico-chemical properties have been investigated. 

From the degree of solvation it is possible to distinguish between two-dimensional and three-dimensional solvated phases (Fig. 14.4) [23]. 

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