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The Effect of Ordered Water on a Short, Strong (Speakman-Hadži) Hydrogen Bond

Sudha S. Marimanikkuppam ; Department of Chemistry, University of Minnesota, 207 Pleasant St. S. E., Minneapolis, Minnesota, 55455, U. S. A.
In-Sook Han Lee ; Department of Science Education, Kangweon National University, Chuncheon 200-701, Korea
David A. Binder ; Department of Biochemistry, Albert Einstein College of Medicine, Bronx, New York, 10461, U. S. A.
Victor G. Young ; Department of Chemistry, University of Minnesota, 207 Pleasant St. S. E., Minneapolis, Minnesota, 55455, U. S. A.
Maurice M. Kreevoy ; Department of Chemistry, University of Minnesota, 207 Pleasant St. S. E., Minneapolis, Minnesota, 55455, U. S. A.


Puni tekst: engleski pdf 21.096 Kb

str. 1661-1674

preuzimanja: 220

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Sažetak

We have determined the structures of the sodium, tetrabutylam- monium (TBA) and bis(triphenylphosphoranylidene)ammonium (PNP) salts of the bis(4-nitrophenoxide) anion by X-ray crystallography. The sodium salt is a dihydrate, with the water oxygens coordinated to the sodium cations, and one hydogen from each water hydrogen bonded to one of the bridging oxygens of the anion.
The TBA and PNP salts are anhydrous. Nevertheless the oxygen- oxygen distance is shortest in the sodium salt; 246.5 pm in the sodium salt, 247.5 pm in the TBA salt, and 249 pm in the PNP salt; suggesting that the hydrogen bond is not weakened by the water, and may be strongest in the hydrated salt. (All three compounds show Hadži type ii IR spectra, and are called Speakman-Hadži compounds in this paper.) The 2H chemical shifts of the bridging hydrogen in the three solids are 16.8 ppm for the sodium salt, 16.8 ppm for the TBA salt, and 16.5 ppm for the PNP salt. Again there is no evidence that the water weakens the hydrogen bond. These results can be understood by noting that the additional hydrogen bonds to the bridging oxygens decrease their proton affinity, but the mutual repulsion of the oxygens is also decreased.

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Hrčak ID:

135998

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https://hrcak.srce.hr/135998

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