Optimized geometries, vibrational force fields and infrared intensities of methyl-N-(1-naphthyl)-urethane were calculated by HF and DFT (B3LYP) methods with 6-31G basis set. The theoretical force fields were scaled using the scaled quantum mechanical method of Pulay. Then normal mode analysis of the two vibrational force fields was carried our. The calculated infrared spectra were compared with the experimental results of Zavodov in dilute solutions. The average deviations between the experimental and computed frequencies were 37. 8 and 8.68 cm^-^1 for HF/6-31G and B3LYP/6-31G methods, respectively. In addition, the whole vibrations modes were assigned according to the calculated potential energy distribution and the infrared intensities.

Key words: NAPHTHALENE P, CARBAMIC ACID ESTER P, GEOMETRICAL ISOMERISM, VIBRATIONAL SPECTRUM, NORMAL COORDINATE ANALYSIS