Direct Observation of Chloride Transfer across the Water/Organic Interface and the Transfer of Long-Chain Dicarboxylates

Abstract

We have extended the negative side of the potential window by using the organic reference electrode Ag/AgTPB and a low supporting electrolyte concentration in the aqueous phase. We have observed directly, for the first time, the voltammetric wave of chloride transferring across the water(W)/1,2-dichloroethane (1,2-DCE) and the water/nitrobenzene (NB) interfaces. The standard potentials (and the standard Gibbs free energies of transfer) have been evaluated by consideration of half-wave potentials, the variations of the activity coefficients in both phases, and ion-pair formation. Our best estimate for the free energy of Cl- transfer to water-saturated 1,2-DCE is 45−46 kJ/mol, and for NB 38 ± 2 kJ/mol. The Gibbs free energies of transfer of a homologous series of long-chain dicarboxylates have also been obtained for the first time. They show a similar dependence on carbon number as monocarboxylates. The transfers of the singly and doubly ionized dicarboxylic acids can also be observed simultaneously when th...