Electronic structure investigations of 4-methyl-3-penten-2-one by UV–Visible and NMR spectral studies and natural bond orbital analysis by DFT calculations

Comprehensive theoretical and experimental UV–Visible, NMR spectroscopic studies of 4-methyl-3-penten-2-one (4M3P2O) have been carried out by using DFT/B3LYP method with 6-311++G** and aug-cc-pVTZ basis sets. The most stable geometry of the compound has been determined from the PES scan. The temperature dependence of thermodynamic properties has been analysed. The atomic charges, electronic exchange interaction and charge delocalisation of the molecule have been performed by natural bond orbital (NBO) analysis. Molecular electrostatic surface potential, total electron density distribution and frontier molecular orbitals are constructed at B3LYP/6-311++G** level to understand the electronic properties. The charge density distribution and site of chemical reactivity of the molecules has been obtained by mapping electron density isosurface with electrostatic potential. UV–Visible spectrum of the compound, the electronic properties, HOMO and LUMO energies were measured by time-dependent TD-DFT approach. 1H and 13C NMR spectra were recorded and 1H and 13C nuclear magnetic resonance chemical shifts of the molecule were calculated in various solvents and in gas phase by using the Gauge-GIAO method.