Role of Trace Amounts of Water in Transfers of Hydrophilic and Hydrophobic Ions to Low-Polarity Organic Solvents

摘要

A detailed knowledge of ion transfer (IT) mechanisms between water and low-polarity media is crucial for many areas of chemistry and biochemistry such as phase transfer catalysis, separations, and biomembranes. Recent theoretical and experimental studies and molecular dynamics simulations of IT at the interface between two immiscible electrolyte solutions (ITIES) and water/lipid membrane interface improved our understanding of thermodynamics, kinetics, and ion distribution at the phase boundary in these systems. IT experiments at nanometer-sized ITIES revealed mechanistic differences between the transfers of relatively hydrophobic and strongly hydrophilic ions: the former can be viewed as unassisted, one-step reactions, while the latter processes have to be facilitated by hydrophobic counterions present in organic phase (shuttling mechanism). Here we show another important mechanistic difference between the two classes of ITs: relatively hydrophobic ions are transferred into neat organic solvents (e.g., 1,2-dichloro-ethane, DCE), but hydrophilic ions can only be transferred to water clusters dispersed in organic phase.