Polarized Raman and Infrared Spectra of [1H4]- and [2H4]Pyridazines

Abstract

The polarized Raman and infrared spectra of [1H4]- and [2H4]pyridazines were studied. Assignments of the normal vibrations made by previous workers were reexamined on the basis of polarization behavior of the Raman and infrared bands and also through the normal coordinate calculation, and reasonable assignments are presented.

Vibrational spectrum of pyridazine

“…5) point to a fundamental of symmetry, A 1 which is contrary to the assignment in Ref. 40, where it is identiÐed as a B-type contour and is assigned as a B 2 fundamental.…”

“…Moreover, three "extraÏ scale factors were also applied for certain o †-diagonal force constants. With help of their SQM force Ðeld, the experimental assignments of Ozono et al 40 were basically conÐrmed. However, assignments were changed in six and four cases for and respecpyridazine-h 4 -d 4 , tively.…”

“…4) and with the polarized Raman band at 963 cm~1. The last ring deformation normal modes, and l 9 (A 1 ) l 24 (B 2 ), were assigned at 632 and 663 cm~1, respectively, by Ozono et al 40 on the basis of the B-type contour for the high wavenumber. These results are not in agreement with the calculations of Be rces et al 28 and Jordan and Parmenter,37 which reversed the assignment.…”

Vibrational Spectra of the Azabenzenes Revisited: Anharmonic Force Fields

“…[54] agree on an assignment to the 1570 cm −1 band. Our results, however, would seem to indicate that the assignment around…”

“…A discussion of these modes is almost impossible, and with the exception of Refs. [53,54] for ν 13 , all experimental assignments lie beyond the likely error bars of the theoretical values.…”