Molecular structure, vibrational spectra and HOMO, LUMO analysis of 4-piperidone by density functional theory and ab initio Hartree-Fock calculations

Abstract

Vibrational frequencies and geometrical parameters of 4-piperidone (4-PID) in the ground state have been calculated by using the Hartree-Fock (HF) and density functional methods (B3LYP) with 6-311++G(d,p) and 6-311+G(3df,2p) basis sets. These methods are proposed as a tool to be applied in the structural characterisation of 4-PID (C5H9NO). The title molecule has C-s point group symmetry, thus providing useful support in the interpretation of experimental IR and Raman data. The DFT-B3LYP/6-311+G(3df,2p) calculations have been found more reliable than the ab initio HF/6-311++G(d,p) calculations for the vibrational study of 4-PID. The calculated highest occupied molecular orbital and lowest unoccupied molecular orbital energies show that charge transfer occurs within the molecule. The theoretical spectrograms for FT-IR and FT-Raman spectra of the title molecule have been constructed.