ACIDITY AND BASICITY SCALES FOR POLAR-SOLVENTS

Acidity and basicity scales for polar solvents are examined and compar ed with the mean spherical approximation parameters derived from the G ibbs energy of solvation of the alkali metal and halide ions in 18 pol ar solvents, both protic and aprotic. On the basis of an analysis of d ata for the Gibbs energy of transfer of 1-1 electrolytes and standard redox potentials for simple reactions in a variety of these solvents, it is concluded that the most appropriate scales are the acceptor numb er AN and donor number DN introduced by Gutmann. The extrathermodynami c assumption for separating cationic and anionic contributions to ther modynamic quantities for electrolytes based on equal solvation of the tetraphenylarsonium and tetraphenylborate ions is reexamined. This ass umption appears to be valid in aprotic solvents but questionable for p rotic ones.