The transfer of neutral molecules, ions and ionic species from water to ethylene glycol and to propylene carbonate; descriptors for pyridinium cations

Abstract

Equations have been constructed for the transfer of neutral solutes from water to the solvents ethylene glycol and propylene carbonate. These equations have been extended to include ions and ionic species derived from acids by loss of a proton and bases by acceptance of a proton. Only one additional term is needed for cations and one additional term for anions. The data used include literature data on the partition coefficients of simple ions, and literature data on pK_a values for carboxylic acids and amines in water, ethylene glycol and propylene carbonate from which we derive ionic partition coefficients. Descriptors have been obtained for 22 substituted pyridinium cations, and equations derived for the prediction of descriptors for further substituted pyridinium cations. Some of the pyridinium cations are the strongest hydrogen bond acids that we have encountered.