VIBRATIONAL-SPECTRUM OF PYRIDAZINE

The infrared spectrum of pyridazine (1,2-diazine) was obtained in the pure liquid and in solution (4000-200 cm(-1)), in the gas phase and as a polycrystalline film (4000-400 cm(-1)). Additionally, the Raman spe ctrum of the liquid together with qualitative depolarization ratios we re obtained. Using the new experimental evidence, an ab initio scaled computation of the vibrational spectrum at the HF/3-21G and HF/6-31G* levels of theory clarified the spectral regions most often discussed in the literature. The IR spectra in CS2 and CCl4 solutions showed a splitting in the CH stretching region. The IR spectrum in polycrystall ine film together with the scaled calculations were decisive in the as signment of the A(2) fundamentals. The IR spectrum in the gas phase sh owed, first, an A-type contour at 665 cm(-1) which determined the nu(9 ),(A(1)) and nu(24)(B-2) assignments and, second, the lowest wavenumbe r ring vibration nu(23), at 1027 cm(-1) which was related to the band at 1043 cm(-1) in polycrystalline film. (C) 1998 John Wiley & Sons, Lt d.