A comparison of nonspecific solvent scales. Degree of agreement of microscopic polarity values obtained by different measurement methods

Abstract

The active role of solvents in physicochemical processes in solution has been long recognized. Different solvatochromic empirical scales are aimed at describing and quantifying the nonspecific interactions at a molecular level. This work presents a new insight into the comparison of the famous ET(30) (Dimroth-Reichardt) and ð* (Kamlet, Abboud, Taft) solvatochromic scales. These parameters were tested against the data derived from theoretical solvent-induced shifts in the UV-vis spectra of the corresponding reference solutes (Matyushov et al.). In each case we centered the attention on the analysis of the degree of agreement between paired values quantified through both scales by applying the methodology described by J. M. Bland and D. G. Altman. In addition, the linear correlations are assessed. The study reflects that a) the scales involved in this comparison are clearly dependent on the type of probe used to quantify the solvent property, and b) the experimental parameters, in general, do not agree with the theoretical ones. These results were related with the contributions of induction, dispersion and dipole-dipole forces to the overall solvent effect. It is expected that the results will be contribute to the evaluation of the ability of the microscopic chemical scales to describe the solute-solvent interactions.