Far-Infrared Spectra and Hydrogen-Bond Frequencies of Imidazole

Abstract

Far‐infrared spectra of imidazole, imidazole‐$d$ ₄, 1‐methyl imidazole, and 1‐methyl‐$d_3$ imidazole have been examined in the 300 − 33‐cm^− 1 range. Six of the nine infrared‐active lattice modes of crystalline imidazole have been observed and assigned. A tentative assignment of these frequencies in terms of hydrogen‐bond motion is given. Far‐infrared spectra of solid and liquid imidazole and its methyl derivatives are compared and discussed. There is no obvious relationship between the hydrogen‐bond frequencies and the structure of the $\nu \mathrm{NH}$ absorption band of crystalline imidazole.