Experimental and theoretical investigation of 1-acetylpiperazine by vibrational spectroscopy

Vibrational spectra of 1-acetylpiperazine (1-ap) were experimentally reported. The conformational analysis, structural parameters, vibrational frequencies, assignments, potential energy distributions (PED) and spectra, some thermodynamics properties and frontier molecular orbitals of 1-ap (C6H12N2O) were theoretically examined by means of B3LYP hybrid density functional theory (DFT) method together with 6-31++G(d,p) basis set. Calculations are assumed for six conformations of 1-ap, both in gas and in solution phase. In order to investigate the solvent effect, benzene as non-polar solvent and methanol as polar solvent were used. Conformational investigation was supported by analysis of the potential energy surface (PES). It was seen that the obtained experimental and theoretical results for 1-ap are in good agreement with each other. The quantum mechanical calculations applied are well and sufficient levels for vibrational frequencies and corresponding vibrational assignments. Normal chair conformation with equatorial substituents is not preferred due to the steric interaction. Vibrational frequencies, assignments and intensities of 1-ap depend on the solvent whereas its conformation is solvent independent. Findings of the research will be useful for studies relevant to the conformers of piperazines. Keywords: 1-acetylpiperazine, Vibrational spectra, DFT, B3LYP, PED, PES.