Zusammenfassung
Dielectric relaxation spectra have been measured for aqueous solutions of sodium malonate and sodium succinate over a wide range of frequencies ( 0.2 <= n/GHz <=89) and solute concentrations (0.025 <= c/M <= 1.0). In addition to the usual processes associated with bulk water, two further relaxation processes were detected. The faster of these, with a relaxation time of ~16 ps, is unusual and was ...
Zusammenfassung
Dielectric relaxation spectra have been measured for aqueous solutions of sodium malonate and sodium succinate over a wide range of frequencies ( 0.2 <= n/GHz <=89) and solute concentrations (0.025 <= c/M <= 1.0). In addition to the usual processes associated with bulk water, two further relaxation processes were detected. The faster of these, with a relaxation time of ~16 ps, is unusual and was attributed to the presence of 'slow' water in the hydration shells of the anions. The extent of this hydration shell is rather 'fragile' (concentration-dependent) for malonate but not for succinate. The second, slower, process was attributed to the presence of ion pairs NaX-(aq). Unambiguous determination of the structure of the ion pair was not possible because of the internal flexibility of the anions but the data were most consistent with a chelated solvent-shared ion pair. The kinetics of formation and dissociation of the ion pairs were evaluated from the effects of solute concentration on their relaxation times.
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