The molecular structure and vibrational spectra of 2-chloro-N-(diethylcarbamothioyl)benzamide by Hartree–Fock and density functional methods

2-Chloro-N-(diethylcarbamothioyl)benzamide (C12H15ClN2OS) has been synthesized and characterized by elemental analysis and IR spectroscopy. The crystal and molecular structure of the title compound has been determined from single crystal X-ray diffraction data. It crystallizes in the orthorhombic space group Pbca, Z = 8 with a = 9.581(3) Å, b = 9.992(3) Å, c = 26.640(8) Å, V = 2550.5(13) Å3 and Dcalc = 1.410 Mg/m3. The molecular geometry and vibrational frequencies of 2-chloro-N-(diethylcarbamothioyl)benzamide in the ground state have been calculated using the Hartree–Fock and density functional using Becke's three-parameter hybrid method with the Lee, Yang and Parr correlation functional (B3LYP) methods with 3-21G and 6-31G(d) basis sets. The calculated geometric parameters were compared to the corresponding X-ray structure of the title compound. The raw B3LYP frequencies approximate the experimental data much better than the results of Hartree–Fock. The scaled B3LYP/6-31G(d) results were more reliable than those obtained using the B3LYP/3-21G method with the mean absolute deviation about 13.7 cm−1. On the basis of the comparison between calculated and experimental results, assignments of fundamental vibrational modes were examined.