Vibrational spectrum of pyridazine

Abstract

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 spectrum of the liquid together with qualitative depolarization ratios were 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 polycrystalline film together with the scaled calculations were decisive in the assignment of the A2 fundamentals. The IR spectrum in the gas phase showed, first, an A-type contour at 665 cm-1 which determined the ν9(A1) and ν24(B2) assignments and, second, the lowest wavenumber ring vibration ν23 at 1027 cm-1 which was related to the band at 1043 cm-1 in polycrystalline film. © 1998 John Wiley & Sons, Ltd.