Solvent polarity and solvation effects in highly aqueous mixed solvents. Application of the <i>Dimroth‐Reichardt</i> E_T(30) parameter

Abstract

Abstract The Dimroth‐Reichardt solvent parameter E T (30) and its temperature dependence (25‐50°C) have been measured in water‐rich mixtures of water with acetonitrile (MeCN), 1,4‐dioxane (1,4‐D), dimethyl sulfoxide (DMSO), tert ‐butanol (TBA) and 2‐ n ‐butoxyethanol (2‐BE). Thermodynamically nonideal behavior of the solutions is indicative for preferential solvation of the probe molecule by all organic cosolvents used. However, the effects are most pronounced for TBA and 2‐BE. This leads to ambiguities in the use of the E T (30) value as an indicator of “solvent polarity” for these aqueous binary mixtures. The temperature dependence of E T (30) in TBA‐H 2 O and 2‐BE‐H 2 O above the critical hydrophobic interaction concentration is interpreted in terms of binding of the probe to small, temperature‐sensitive aggregates of the cosolvent.