Solute–solvent and solvent–solvent interactions in binary solvent mixtures. Part 6. A quantitative measurement of the enhancement of the water structure in 2-methylpropan-2-ol–water and propan-2-ol–water mixtures by solvatochromic indicators

Abstract

A preferential solvation model that takes into account the enhancement of the structure of water when small amounts of alcohol are added is proposed and tested for solvatochromic indicators in binary mixtures of 2-methylpropan-2-ol and propan-2-ol with water. The model modifies an equation previously developed for solvatochromic indicators in binary solvent mixtures. The new model includes a correction term for the effect of the enhancement of the water structure on the measured solvatochromic property that allows a quantitative estimation of this effect. It is shown that the enhanced water structure is more polar and has a larger hydrogen-bond donor capability, but a smaller hydrogen-bond acceptor ability, than the common water structure.