Molecular structure, intramolecular hydrogen bonding and vibrational spectral investigation of 2-fluoro benzamide – A DFT approach

Abstract

The FTIR and FT-Raman spectra of 2-fluoro benzamide (2FBA) have been recorded in the region 4000–400 and 4000–100cm−1, respectively. The structuralanalysis, hydrogen bonding, optimized geometry, frequency and intensity of the vibrational bands of 2FBA were obtained by the density functional theory (DFT) with complete relaxation in the potential energy surface using 6-31G** basis set. The harmonic vibrational frequencies were calculated and the scaled values have been compared with experimental FTIR and FT-Raman spectra. The observed and the calculated frequencies are found to be in good agreement. The 13C NMR spectra have been recorded and 13C nuclear magnetic resonance chemical shifts of the molecule were also calculated using the gauge independent atomic orbital (GIAO) method and their respective linear correlations were obtained. The electronic properties, such as HOMO and LUMO energies, were performed by time-dependent DFT (TD-DFT) approach. The Mulliken charges, the values of electric dipole moment (μ) of the molecule were computed using DFT calculations. The change in electron density (ED) in the σ* antibonding orbitals and stabilization energies E(2) have been calculated by natural bond (NBO) analysis to give clear evidence of stabilization originating in the hyper conjugation of hydrogen–bonded interactions.