Spectroscopic investigation and natural bond orbital analysis on 4-ethylmorpholine

• The FT-IR and FT-Raman spectra of 4-ethylmorpholine have been recorded. • The complete assignments are performed on the basis of the potential energy distribution (PED). • HOMO–LUMO energies, molecular electrostatic potential distribution of the molecule were calculated. • Stability of the chair conformation has been analyzed using NBO analysis. This study is an analysis of FT-IR (4000–400 cm −1 ) and FT-Raman (4000–0 cm −1 ) spectra of 4-ethylmorpholine (4EM). The molecular geometry, vibrational frequencies, infrared intensities, Raman activities and atomic charges have been calculated by using ab initio HF and density functional theory calculation (B3LYP) with 6-311+G(d,p) basis set. Complete vibrational assignment and analysis of the fundamental modes of the compound were carried out using the observed FT-IR and FT-Raman spectra for 4EM. NBO analysis has been performed on the before and after flipping the chair conformation of 4EM at DFT method. The formation of the hydrogen bond was investigated using NBO calculations. The dipole moment ( μ ) and polarizability ( α ), anisotropy polarizability (Δ α ) and hyperpolarizability ( β ) of the molecule have been reported. The theoretical UV–Visible spectrum of the compound was computed in the region 200–400 nm and the electronic properties HOMO and LUMO energies were measured by time-dependent TD-DFT approach. Thermodynamic properties (heat capacity, entropy and enthalpy) of the title compound at different temperatures were calculated.