Vibrational spectra of pyrazole and deuterium‐substituted analogues

Accurate vibrational frequencies are reported for pyrazole and for seven N‐ and C‐deuterated analogues from FT‐IR spectra for the vapour phase at room temperature, diluted CCl4 solutions and polycrystalline solids and from Raman spectra in aqueous solutions. Several frequencies are reported for fundamentals not previously observed in the vapour phase in particular. Assignments were carried out by performing a normal coordinate analysis for in‐plane and out‐of‐plane modes, using either Urey–Bradley or general valence force fields. Great care was taken to determine a refined force constant set which agrees as far as possible with observed isotopic shifts. A detailed description of all the normal modes and atomic displacements for in‐plane modes is given.