Natural bond orbital analysis, electronic structure and vibrational spectral analysis of N-(4-hydroxyl phenyl) acetamide: A density functional theory

• FT-IR, FT-Raman and UV–vis spectra of N4HPA in the solid phase were recorded and analyzed.
• The PED calculation provides a strong support for the frequency assignment.
• NBO analysis used to explain the interaction between electron donors and acceptors.
• HOMO and LUMO energies, MESP distribution of the molecule were calculated.
• Chemical shift of the title compound were found.

The Fourier transform infrared (FT-IR) and FT-Raman spectra of N-(4-hydroxy phenyl) acetamide (N4HPA) of painkiller agent were recorded in the region 4000–450 cm−1 and 4000–50 cm−1 respectively. Density functional theory (DFT) has been used to calculate the optimized geometrical parameter, atomic charges, and vibrational wavenumbers and intensity of the vibrational bands. The computed vibrational wave numbers were compared with the FT-IR and FT-Raman experimental data. The computational calculations at DFT/B3LYP level with 6-31G(d,p), 6-31++G(d,p), 6-311G(d,p) and 6-311++G(d,p) basis sets. The complete vibrational assignments were performed on the basis of the potential energy distribution (PED) of the vibrational modes calculated using Vibrational energy distribution analysis (VEDA 4) program. The oscillator’s strength calculated by TD-DFT and N4HPA is approach complement with the experimental findings. The NMR chemical shifts 13C and 1H were recorded and calculated using the gauge independent atomic orbital (GIAO) method. The molecular electrostatic potential (MESP) and electron density surfaces of the molecule were constructed. The Natural charges and intermolecular contacts have been interpreted using Natural Bond orbital (NBO) analysis the HOMO–LUMO energy gap has been calculated. The thermodynamic properties like entropy, heat capacity and zero vibrational energy have been calculated.

N-(4-hydroxyl phenyl) acetamide (N4HPA) is commonly used for the relief of fever, headaches, and other minor aches and pains, and is a major ingredient in numerous cold and flu remedies. The equilibrium geometry harmonic vibrational frequencies, infrared intensities, Thermodynamic properties, NBO analysis and NMR Spectral analysis were calculated by density functional (B3LYP) method with 6-31G(d,p), 6-31++G(d,p), 6-311G(d,p) and 6-311++G(d,p) basis sets, using Gaussian 09W program. HOMO and LUMO energies are calculated that these energies show charge transfer occurs within the molecule.Figure optionsDownload as PowerPoint slide