Structural study, NCA, FT-IR, FT-Raman spectral investigations, NBO analysis and thermodynamic properties of 2′,4′-difluoroacetophenone by HF and DFT calculations

Abstract

In this work, the vibrational spectral analysis was carried out by FT-IR and FT-Raman spectroscopy in the regions of 4000–400cm−1 and 3500–100cm−1, respectively for 2′,4′-difluoroacetophenone (DFAP). The molecular structure, fundamental vibrational frequencies and intensity of the vibrational bands are interpreted with the aid of structure optimizations and normal coordinate force field calculations based on Hartree–Fock (HF), density functional theory (DFT) using B3LYP and LSDA methods with 6-31G basis set combination. The mixing of the fundamental modes was determined with the help of potential energy distribution (PED). The energies of the frontier molecular orbitals have also been determined. Complete NBO analysis was also carried out using B3LYP/6-31G level of theory to find out the intramolecular electronic interactions and their stabilization energy. Thermodynamic properties of the title compound were calculated at the different temperature. Finally, the calculation results were applied to simulate FT-IR and FT-Raman spectra of the title compound which show good agreement with observed spectra.