Infrared and Raman spectra of heterocyclic compounds—I the infrared studies and normal vibrations of imidazole

The infrared spectra of imidazole and some substituted imidazoles were obtained from 4000 to 33 cm−1. The bands in imidazole are assigned on a basis of comparison with its deuterated and trihalogeno substituted analogs and its metal complexes as well as other aromatic and heteroaromatic systems reported in the literature. A detailed normal coordinate analysis was made for the imidazole molecule considered as a ten-body structure possessing C2v symmetry. Utilizing a Urey Bradley Force Field an approximate description was given for each vibrational mode and values of all the force constants for planar and out of plane vibrations were obtained.