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

2-Chloro-N-(diethylcarbamothioyl)benzamide (C12H15CIN2OS) 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) angstrom, b = 9.992(3) angstrom, c = 26.640(8) angstrom, V= 2550.5(13) angstrom(3) and D-calc = 1.410 Mg/m(3). 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 6-31 G(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/631G(d) results were more reliable than those obtained using the B3LYP/3-21 G 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. (c) 2007 Elsevier B.V. All rights reserved.