L-Phenylalanine was grown by slow evaporation method The FTIR-spectrum of grown crystal was recorded in the regions 4000–450 cm-1.The optimized geometry, harmonic vibrational spectra, wave number and thermodynamic properties of L-Phenylalanine have been computed ab initio Hartee-Fock and DFT method. The calculated harmonic vibrational frequencies were compared with experimental FTIR spectra. Predicted vibrational frequencies have been assigned and they supported each other. Good agreement in terms of both frequencies and intensities were found between the calculated and observed FTIR spectra. On the basis of vibrational analysis the thermodynamic properties of the title compound have been calculated.
