Solvation exchange constant

In this theory the general medium and solvation effects are coupled through the solvation exchange constants K, and K2, which determine the composition of the solvation shell surrounding the solute, and thereby influence the surface tension in the solvation shell. But the situation is actually more complicated than this, for if surface tension-composition data ate fitted to eq. [8.2.26] the resulting equilibrium constants are not numerically the same as the solvation constants Kj and K2 evaluated from a solubility study in the same mixed solvent. Labeling the surface tension-derived constants K j and K 2, it is usually... 

In order to determine the solvation numbers and the exchange constants it is assumed that one (Lys HBr)n residue consists of two parts, namely, the ionic group (numbered 2) and the less polar remainder of the molecule (numbered 1). Plotting... 

It has been shown that the effects found are caused by specific solvation of both the PhAA ionogenic and other polar groups by the plasticizers used, as well as by the influence of ion-exchangers nature on the PhAA cations-anionic sites complex formation constants. 

The definition of solvent exchange rates has sometimes led to misunderstandings in the literature. In this review kjs 1 (or fc2lsolvent]), sometimes also referred to as keJ s 1, is the rate constant for the exchange of a particular coordinated solvent molecule in the first coordination sphere (for example, solvent molecule number 2, if the solvent molecules are numbered from 1 to n, where n is the coordination number for the solvated metal ion, [MS ]m+). Thus, the equation for solvent exchange may be written ... 

The proton exchange is called protolysis solvation as a general term means hydration in the case of water, the dielectric constant (e = 78) of which is so high... 

Where solvent exchange controls the formation kinetics, substitution of a ligand for a solvent molecule in a solvated metal ion has commonly been considered to reflect the two-step process illustrated by [7.1]. A mechanism of this type has been termed a dissociative interchange or 7d process. Initially, complexation involves rapid formation of an outer-sphere complex (of ion-ion or ion-dipole nature) which is characterized by the equilibrium constant Kos. In some cases, the value of Kos may be determined experimentally alternatively, it may be estimated from first principles (Margerum, Cayley, Weatherburn Pagenkopf, 1978). The second step is then the conversion of the outer-sphere complex to an inner-sphere one, the formation of which is controlled by the natural rate of solvent exchange on the metal. Solvent exchange may be defined in terms of its characteristic first-order rate constant, kex, whose value varies widely from one metal to the next. 

In the course of our investigations to develop new chiral catalysts and catalytic asymmetric reactions in water, we focused on several elements whose salts are stable and behave as Lewis acids in water. In addition to the findings of the stability and activity of Lewis adds in water related to hydration constants and exchange rate constants for substitution of inner-sphere water ligands of elements (cations) (see above), it was expected that undesired achiral side reactions would be suppressed in aqueous media and that desired enanti-oselective reactions would be accelerated in the presence of water. Moreover, besides metal chelations, other factors such as hydrogen bonds, specific solvation, and hydrophobic interactions are anticipated to increase enantioselectivities in such media. 

Rate Constants and Activation Parameters for Solvent Exchange on Rhodium(III) and Iridium(III) Solvates ... 

In the treatment of the kinetics of the electron transfer illustrated in Section 4.1, it has been assumed that the propulsive force for the electron transfer was the electrochemical potential E i.e. a quantity directly related to 4>M — < >s). However, since the solvated ions cannot enter the inner layer of the double layer (IHP), the true propulsive force should be < )M — standard rate constant, k°, and the exchange current, i0, should become respectively ... 

The solvent molecules in the primary solvation shell are constantly renewed by a solvent exchange reaction ... 

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