Solvate active component

Selection of the second (indifferent) component s e also provides means to control the universal solvation ability of mixed solvent. In the above mentioned examples, increasing the solvate inert component concentration results in the decrease of mixed solvent 8. On the contrary, addition of indifferent component (propylene carbonate) into the systems such as acetic acid-propylene carbonate or propylene carbonate-aniline causes 8 to rise. Because in the last two systems acetic acid and aniline were chosen as solvate active components, it was obviously intended to use these mixtures for specific solvation of the dissolved donor and acceptor compounds respectively. 

For binary solvents formed by solvation (active component A and indifferent component B) analysis of equation [9.52a] demonstrates that there is also a linear correlation between InK and 1/e. Such mixed solvents are proposed to be called as conventionally universal. 

Only when A is a solvate-active component in the mixed solvent A-B, in the general case, both A and B initial components undergo specific solvation ... 

Concentration of the solvate active solvent or the solvate active component A of mixed solvent in dilute solution is higher than the initial concentration of equilibrium components [E]o and [F]q. Then activity of equilibrium components is equal to their concentrations. Then equations of material balance for components A and B can be set down as... 

Although the solvate-active components are weak bases, their differences influence... 

According to the above energy characteristics of the heteromolecular association process (resolvation) in specific media, the solvent exchange affects the products output (the relationship of output c and K s is estimated from the equation [9.66]). This shows that the product output (with initial concentration of reagents 0. IM) can be changed from 34% (pure heptane) to 4 % (pure n-chlorotoluene) by changing the binary mixed solvent composition. The processes [9.85a] and [9.85] can be eliminated completely when the solvate active component (more basic then chlorotoluene) is used. 

It is easy to develop the equation for binary solvent formed from two solvate-active components similar to [9.90] by using the above scheme for the binary solvent with one solvate active component (equations [9.76 - 9.80]) and introducing equilibrium constant of... 

The reaction [9.104] also has been studied for isodielectric mixtures of alcohol-chlorobenzene with 8=20,2 (permittivity of pure n-propanol) and 8=17.1 (permittivity of pure n-butanol) to investigate flic relative effect of universal and specific solvation on the resolvation process. The mixtures were prepared by adding chlorobenzene to methanol, ethanol, and C1-C3 alcohol. Alcohol is a solvate-active component in these isodielectric solvents. K s data are given in Table 9.6. 

The change of donor property of the solvate-active component is not signifieant. The equations relating Kug to 8 permit to divide free energy of resolvation process into the components. Corresponding data are presented in Table 9.7. 

A similar phenomenon is observed in conditionally-universal media A-B (A is solvate-active component, B is solvate-inert component). Association constant can be eal-culated from equations [9.56] or [9.104] for LiBr and KCNS solutions. ... 

The dependence of luK and 1/8 for LiBr in mixed solvent [9.53] shows an influence of solvate-active component on K. The difference of LiBr solvation energy in the presence of pyridine and acetic acid may be evaluated in accordance to [9.53], assuming low solvation energy of LL by propylene carbonate in comparison with pyridine and negligible value of solvation energy of anion in solvents containing dichlorobenzene (DCB) and pyridine. 

The degree of ion association of acids as well as ionophores depends significantly on solvents permittivity. The influence of the specific solvation by the solvate active component is pertinent from the comparison InK - l/e isotherms for acid solutions in conditionally universal media... 

General analysis of the binary solvent mixtures formed by two solvate active components (these solvents are often used in analytical and electrochemistry) was conducted to evaluate their effect on H-acids. The analysis was based on an equation which relates the constant of ion association, K, of the solvent mixture and constants of ion association of the acid Kj and K of each component of the mixed solvent, using equilibrium constants of scheme [9.105] - heteromolecular association constant, ionization constant of the... 

The data for cadmium thiourea complexes in water-methanol mixed solvent are presented in Table 9.14. Dependence of stability constant on the solvent composition is very complex in the mixed solvents formed by two solvate-active components as defined by the relative activity, L, of A and B. Dependencies of stability constant for some complexes in water-B solution (where B is methyl acetate, methanol, etc. ) are presented in Figures 9.21 and 9.22 for complex NiEn (En=ethylenediamine) in water-non-aqueous solution (the constants are presented relative to stability constant in water). 

Although the solvate-active components are weak bases, their differences influence the values AG -aG5X,xNB and crGg Pi. The first value characterizes the difference between the covalent components of solvation energy for trinitrobenzene in any solvate-active solvent. It follows from the table, that contributions of the covalent and electrostatic components are comparable in the whole concentration range of the mixed solvents. This indicates the same influence of both donor property and permittivity of the solvent on the [8.1.85a] process equilibrium. 

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