The FTIR and FT Raman spectrum of propylthiouracil has been recorded in the regions 4000 – 400 cm-1 and 3500 – 100 cm-1, respectively. The optimized geometry, wave number and intensity of the vibrational bands of propylthiouracil were obtained by ab initio and DFT levels of theory with complete relaxation in the potential energy surface using 6-31G (d,p) basis set. A complete vibrational assignment aided by the theoretical harmonic frequency analysis has been proposed. The harmonic vibrational frequencies calculated have been compared with experimental FTIR and FT Raman spectra. The observed and the calculated frequencies are found to be in good agreement. The experimental spectra also coincide satisfactorily with those of theoretically constructed bar type spectrograms
