A Comparison of the Temperature Dependent 1H NMR and Empirical Force Field Techniques in Determining Enantiomeric Recognition of Organic Ammonium Salts by Chiral Di- and Tetraalkyl-Substituted Pyridino-18-Crown-6 Ligands.
BRIGHAM YOUNG UNIV PROVO UT DEPT OF CHEMISTRY
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Complexation of the R- and S- forms of alpha-1-naphthyl ethylammonium perchlorate by chiral pyridino-18-crown-6 ligands 1-6 has been studied by the temperature dependent 1H NMR technique. At low temperatures, the peaks in the H NMR spectra of the complexes attributable to the hydrogen atoms on the CH2 groups attached to the pyridine rings centered at about sigma 4.5, or the methyl hydrogens in the cases of 5 and 6, separated into two peaks of equal intensities. The low temperature peak separations were 40-140 Hz. At high temperatures, the appearance of a single peak is caused by a fast intermolecular or intramolecular face to face guest exchange. The kinetic parameters for the dissociation of these complexes were calculated reported.
- Organic Chemistry