An experimental study and computation of the infrared absorption spectrum of 3,5-dimethyl-4-phenylpyridine

The infrared absorption spectrum of 3,5-dimethyl-4-phenylpyridine in the 400–2000 cm^–1 range was obtained. A valence-force model was used to compute the fundamental frequencies and normal vibrational modes. The experimental and computed data were found to be in good agreement. The addition of two methyl groups in the 3,5-positions of the-phenylpyridine molecule reduces conjugation between the benzene and pyridine rings, rendering the molecule noncoplanar. The free rotation of the methyl groups about the C-C bond is retarded by the free electron pair in the nitrogen atom of the pyridine ring.