Normal Coordinates of the Planar Vibrations of Pyridine and Its Deuteroisomers with a Modified Urey—Bradley Force Field

Abstract
A Urey—Bradley potential function has been fitted to the observed vibrational frequencies of pyridine, pyridine‐2,6‐d2, pyridine‐3,5‐d2, pyridine‐4‐d1, and pyridine‐d5. As in the case of benzene, it was necessary to include an additional non‐Urey—Bradley force constant ρ to describe the aromatic character of the molecule. Our results suggest several minor changes in the vibrational assignment of some of these molecules.
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