Self-Association of Water and Water−Solute Associations in Chloroform Studied by NMR Shift Titrations
| Autor: | Frank Eblinger and, Hans-Jörg Schneider |
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| Rok vydání: | 1996 |
| Předmět: | |
| Zdroj: | The Journal of Physical Chemistry. 100:5533-5537 |
| ISSN: | 1541-5740 0022-3654 |
| Popis: | Association constants and the corresponding free energies ΔG were obtained by nonlinear least-square fitting of the water 1H NMR shift changes observed at different concentrations. The only until now available earlier value (Shaw, J.-H. L.; Wang, S. M.; Li, N. C. J. Phys. Chem. 1973, 77, 236) is shown to be based on erraneous evaluations and on inaccurate data. Analysis for the self-association of water in chloroform based on a 1:1 dimer model yields ΔG = −3.5 kJ/mol; based on a trimer model one obtains an almost equally good fit with ΔG = −15.4 kJ/mol. The ΔG value in acetonitrile as solvent is with +9 kJ/mol positive (vide infra) as are all ΔG values observed for water−solute associations in chloroform with DMF, DMSO, diphenyl sulfoxide, and benzene, with the exception of HMPT (hexamethylphosphotriamide) and a special diamide designed to take up water by 2 hydrogen bonds. The complexation induced shifts, determined simultaneously from the NMR titrations, are between 3 and 4.5 ppm. They are similar to th... |
| Databáze: | OpenAIRE |
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