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

Abstract

The effect of water content in a low polarity organic phase on transfers of hydrophobic and hydrophilic ions across the liquid/liquid interface was investigated by nanopipet voltammetry. It was shown recently (J. Am. Chem. Soc. 2006, 128, 15019) that hydrophilic ions can be transferred to less polar solvents such as 1,2-dichloroethane (DCE) only in the presence of organic counterions that facilitate such processes. The addition of trace amounts of water to neat DCE induces the transfers of hydrophilic ions but practically does not affect the transfers of hydrophobic species. Although the conductivity of neat DCE decreases upon addition of water to it, the rates of hydrophilic ion transfers increase markedly with increasing concentration of water in organic phase. This observation suggests different transfer mechanisms for hydrophobic and hydrophilic ions: while the former are transferred directly into neat organic solvents, the latter can only be transferred to aqueous clusters dispersed in organic phase.