Solvent coordinating property and electron-donor ability

Solvent coordinating property and electron-donor ability 

According to chemical properties, solvents can be divided into electron donors and electron acceptors. An electron-donor solvent (D) will react with an electron-acceptor solvent (A), as shown in the following examples  

On the other hand, an electron-acceptor solvent (A) reacts with an electron-donor solvent (D). Since the anions are usually electron-pair donors, the reaction of solvent (A) and the anion will take place as follows  

The quantitative measure for the electron-donating ability of solvents is adequately given by reaction enthalpy e.g., for reaction (1.11.11) it is [D SbCl5]. Very diluted solutions are used in practice so that gas laws can be applied. Changes in the Gibbs energy (AG°) can be determined by spectroscopic and NMR measurements, thus enabling determination of the equilibrium constants of reactions with certain solvents. A linear relationship has 

It is generally taken that -A f[D SbCl5] values yield useful information on the degree of interaction between an electron-donor solvent (D) and the chosen substrate (SbCls). The number ascribed to a solvent to indicate its electron-donor ability bears the symbol 

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