Nuclear Overhauser effect kinetics

In contrast, with axle 15 only one orientation is observed at low temperature, even after 70 days. The assignment of the orientation could be obtained by the observation of ROESY (rotating frame nuclear overhauser effect correlation spectroscopy) cross-peaks between C5H CD protons and the 3-methylpyridine site and, conversely, the C3H CD protons with the site containing the disubstituted pyridine. However, increasing the temperature to 343 K equilibration takes place and the two orientations become equally populated, showing that the observed selectivity had a kinetic origin. 

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