SOLVATOCHROMIC PARAMETERS FOR BINARY-MIXTURES AND A CORRELATION WITH EQUILIBRIUM-CONSTANTS .1. DIOXANE-WATER MIXTURES

The values of the solvatochromic parameters-alpha and beta were determined at 25-degrees-C for dioxane-water mixtures from 0 to 100% of dioxane. These values as well as those of the Reichardt polarity parameter E(T)(30) and the polarity-polarizability pi* are correlated with acid dissociation constants and other equilibrium constants in solvent mixtures of the same composition. As a general rule, two linear zones with different slopes are obtained, one zone covering water-rich solutions, and the other dioxane-rich solutions. The change in behavior takes place at about 55% (v/v) dioxane for all equilibria studied. A fit of pK to an equation of the multiparametric form proposed by Kamlet and Taft shows in most cases a linear dependence on pi* alone, in other cases a dependence on pi* and beta.