Theoretical studies on molecular conformers and infrared spectra of triethylamine

Abstract

<sec>Based on the method of density functional theory B3LYP with a 6-311++G(d, p) basis set, the potential energy surface of conformational isomerization along the two-dimensional coordinates formed by the dihedral angles <i>ϕ</i>₁(C9N1C2C5) and <i>ϕ</i>₂(C16N1C9C12) in a range of –180°–180° is investigated. And 12 ground state conformers of triethylamine are identified. Furthermore,with the second-order Moller-Plesset perturbation theory</sec><sec>MP2 on the same basis set level, the structures of six lower-energy conformers are optimized and their energy values are estimated. The results show that G1 and G1' with C₃ symmetry are the most stable conformers and G4 and G4' with new methyl orientations are identified. In addition, some vibrational modes in the infrared spectra of G1–G4 are assigned and discussed. The infrared spectra of G1–G4 show that the intensity is weak in a range of 0–1600 cm^–1, while the intensity is strong in a range of 2800–3300 cm^–1. The characteristic vibration modes such as umbrella vibration and CH stretching vibration are assigned. The average shift of the corresponding infrared peaks on different conformations is estimated at less than 20 cm^–1.</sec>