Empirical parameters for donor and acceptor properties of solvents

Interactions between solute and solvent lead to induced changes in bond parameters due to coordination whose effects are manifested equally in both the solvent and the solute. In contrast to the existing “one-parameter approaches” a clear distinction is made between nucleophilic and electrophilic solvent functions towards the solute. In the presented “two-parameter approach” two empirical parameters are used namely the donicity or donor number (DN) to describe the nucleophilic behaviour and the acceptor number (AN) to describe electrophilic behaviour on the part of the solvent. Numerous semi-quantitative relationships have been found between each of these solvent parameters and a great variety of solution properties. Rules are presented which are extremely useful in choosing the most suitable solvent for a particular purpose.