Partition of solutes from the gas phase and from water to wet and dry di-n-butyl ether:: a linear free energy relationship analysis

From literature data and from our own measurements, we have compiled a database of partition coefficients of non-electrolytes from water to wet di-n-butyl ether (DBE) and dry DBE, and from the gas phase to wet DBE and to dry DBE. Application of the general linear free energy relationship solvation equations shows that there are small, but significant, differences in the solvation behaviour of wet and dry DBE. In particular, the partition of acidic solutes into wet DBE is favoured over partition into dry DBE. An analysis based on the water-dragging effect of Testa et al. (J. Am. Chem. Soc., 1993, 115, 963) accounts quantitatively for this difference, which is shown to be due to complexation between acidic solutes and water acting as hydrogen bond base. It is suggested that even minute quantities of water may influence the solvation behaviour of non-polar solvents towards specific classes of solute.