ISSN:
1572-8927
Keywords:
23Na+ and81Br− NMR relaxation
;
ion-solvent interactions
;
preferential solvation
;
H2O + amide mixtures
;
hydrophobic effects
;
formamide
;
N-methylformamide
;
N,N-dimethylformamide
Source:
Springer Online Journal Archives 1860-2000
Topics:
Chemistry and Pharmacology
Notes:
Abstract Ion-solvent interactions of Na+ and Br− in binary aqueous mixtures of formamide,N-methylformamide (NMF), andN,N-dimethylformamide (DMF) are studied by use of23Na and81Br magnetic relaxation times, extrapolated to zero salt concentration. The relaxation times, which are controlled by quadrupolar interaction, have been measured over the complete mixture range and are compared with a simplified theoretical formula. It turned out that the23Na+ relaxation in H2O-formamide and H2O-NMF mixtures is in excellent agreement with theoretical predictions, implying nonpreferential solvation of Na+ in these systems. Small deviations of experimental from theoretical results in H2O+DMF possibly indicate weak selective hydration of the cation. In the case of the anionic nuclei81Br−, deviations from the theoretical curve occur which are to be expected, especially for systems where hydrophobic effects play a role. On the other hand, it is demonstrated that these deviations can easily be explained within the electrostatic theory by differences in structural details of the anionic solvation sphere in the mixtures compared to the pure solvents.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00652020
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