Pyridine and its derivative compounds have been extensively studied from the spectroscopic point of view, mainly due to its presence in many chemicals of high interest in a variety of biomedical and industrial fields. The vibrational spectra of pyridine and its derivatives have been considered by several groups [1-13] and many discrepancies have been reported. The aim of the present work is a new normal coordinate analysis based on the B3LYP/6-311++G** calculation to shed light on the discrepancies between reported assignments. In addition, to make an unambiguous assignment, anharmonic vibrational frequencies were also calculated at the same level of theory.

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