A unified scale of solvent polarities for specific and non-specific interactions

Abstract

A unified scale for predicting non-specific solvent polarity employs the physicochemical properties of solutes, such as NMR, EPR, electronic transitions, etc., and the equation Δχ=S′P+W in order to produce a scale of non-specific solvating ability. This approach is successful due to the exclusion of data for systems where donor–acceptor interactions exist. In this paper, the Unified Scale is extended to include systems in polar acceptor solvents by using the equation Δχ=E_A′E_B+C_A′C_B*+S′P+W, which takes into account both the non-specific and specific donor–acceptor interactions of these solvents with donor solute probes. An experimental procedure which leads to the separation of solute solvation into non-specific and specific components is described.