Zusammenfassung
The cooperative dynamics and hydration of aqueous xylitol solutions were investigated at 25 degrees C by broad-band dielectric spectroscopy for solute concentrations c <= 3.251 M. The spectra could be consistently interpreted by assuming a superposition of five modes. From the combined amplitudes of the bulk-water contributions at similar to 18 GHz and similar to 600 GHz the effective xylitol ...
Zusammenfassung
The cooperative dynamics and hydration of aqueous xylitol solutions were investigated at 25 degrees C by broad-band dielectric spectroscopy for solute concentrations c <= 3.251 M. The spectra could be consistently interpreted by assuming a superposition of five modes. From the combined amplitudes of the bulk-water contributions at similar to 18 GHz and similar to 600 GHz the effective xylitol hydration number of 5.66 +/- 0.08 was derived. These hydrating H2O molecules are retarded by a factor of similar to 2.6 compared to the bulk and cause similar to 85% of the relaxation resolved at similar to 5-10 GHz. The remaining amplitude could be attributed to the three central -OH groups of xylitol, which exhibit slower dynamics than the more exposed distal hydroxyl groups peaking at similar to 50 GHz but all having the same effective dipole moment, mu 0eff = 3.43 D. A further xylitol-specific relaxation at similar to 1.5 GHz probably arises from weak xylitol aggregation.
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