Vibrational assignments of six-membered heterocyclic compounds: Normal vibrations of 6-amino uracil and 6-amino 2-thio uracil

Abstract Infrared spectra of 6-amino uracil (6AU), 6-amino-2-thio uracil (6A2TU) and their N -deuterated derivatives have been measured over the range 4000-200 cm −1 . The fundamental frequencies of these molecules have been assigned on the basis of normal coordinate calculations carried out using a Urey—Bradley potential function supplemented with valence type constants for the out-of-plane modes of the planar skeleton. The results of the vibrational analysis are discussed and correlated with the assignments available for other related molecules.