Ethanol monomer revisited: Thermal isomerisation between anti and gauche conformers in Ar and N 2 matrix

The anti-gauche conformational distribution of ethanol has been investigated using the O-H and symmetric C-C-O stretching infrared spectra in argon and nitrogen matrix. The dipole moment of the gauche conformer is higher compared to the anti conformer. The relative population of the anti and gauche conformer of ethanol depends on the rare gas mixture in the gas phase and also in the matrix after thermal cyclisation. In the gas phase, the anti conformer is more populated in nitrogen mixture whereas the gauche conformer is more populated in the argon mixture. After thermal cyclisation in the matrix, the anti conformer isomerise to the gauche conformer in nitrogen matrix and reverse happens in the argon matrix. Thermal cyclisation at 30 K in nitrogen matrix leads to the splitting of the gauche± states that is probed by monitoring symmetric C-C-O stretching frequency mode. © 2020 Elsevier B.V.