DFT, FT-IR and Raman investigations of 1-pyrrolidino-1-cyclopentene

FT-IR and Raman spectra of 1-pyrrolidino-1-cyclopentene (1py1cp) were experimentally reported in the region of 4000–10 cm−1 and 4000–100 cm−1, respectively. The optimized geometric parameters, normal mode frequencies and corresponding vibrational assignments of 1py1cp (C9H15N) were theoretically examined by means of the B3LYP hybrid density functional theory (DFT) method together with the 6-31++G(d,p) basis set. Furthermore, reliable vibrational assignments were made on the basis of the potential energy distribution (PED) and the thermodynamics functions, the highest occupied and the lowest unoccupied molecular orbitals (HOMO and LUMO) of 1py1cp were predicted. Calculations were carried out employed for three different conformations of 1py1cp in gas phase. Comparison between the experimental and theoretical results indicates that density functional B3LYP method is able to provide satisfactory results for predicting vibrational wavenumbers and envelope conformer is predicted to be the most stable conformer of 1py1cp.

Graphical abstractFigure optionsDownload full-size imageDownload as PowerPoint slideHighlights► FT-IR, Raman and quantum chemical calculations of 1py1ch. ► Geometric conformers of 1py1cp. ► Envelope form of 1py1ch is supposed to be the most stable form. ► DFT/B3LYP level is able to provide satisfactory results for predicting vibrational data.