Comparative vibrational spectroscopic studies, HOMO–LUMO and NBO analysis of N-(phenyl)-2,2-dichloroacetamide, N-(2-chloro phenyl)-2,2-dichloroacetamide and N-(4-chloro phenyl)-2,2-dichloroacetamide based on density functional theory
Abstract The structure and the vibrational frequencies of the fundamental modes of the optimized geometry of N-(phenyl)-2,2-dichloroacetamide (NPA), N-(2-chloro phenyl)-2,2-dichloroacetamide (2CPA) and N-(4-chloro phenyl)-2,2-dichloroacetamide (4CPA) have been determined by DFT/B3LYP method. A detailed vibrational spectral analysis was carried out and the assignments of the observed bands have been proposed on the basis of potential energy distribution (PED). Molecular electrostatic potential (MEP) surface was plotted over the geometry to elucidate the reactivity of the molecule. NBO analysis has been performed in order to elucidate charge transfer or conjugative interaction, the intra-molecule rehybridization and delocalization of electron density within the molecule. The lowest singlet → singlet spin-allowed excited states were taken into account for the TD-DFT calculations in order to investigate the properties of electronic transition. HOMO–LUMO analysis has been done in order to determine the way the molecule interacts with other species. On the basis of vibrational analysis, the thermodynamic properties of the title compounds at different temperatures have been calculated, revealing the correlations between heat capacity ( C p,m ∘ ), entropy ( S m ∘ ), enthalpy ( H m ∘ ) and temperature. Other molecular properties such as ionization energy, electron affinity, chemical potential, global hardness and electrophilicity were also calculated.