Emmeluth Corinna, Dyczmons Volker, Kinzel Tom, Botschwina Peter, Suhm Martin A, Yáñez Manuel
Institut für Physikalische Chemie, Universität Göttingen, Tammannstr. 6, D-37077 Göttingen, Germany.
Phys Chem Chem Phys. 2005 Mar 7;7(5):991-7. doi: 10.1039/b417870j.
The subtle trans-gauche equilibrium in the ethanol molecule is affected by hydrogen bonding. The resulting conformational complexity in ethanol dimer manifests itself in three hydrogen-bonded OH stretching bands of comparable infrared intensity in supersonic helium expansions. Admixture of argon or nitrogen promotes collisional relaxation and is shown to enhance the lowest frequency transition. Global and local harmonic frequency shift calculations at MP2 level indicate that this transition is due to a gauche-gauche dimer, but the predictions are sensitive to basis set and correlation level. Energetically, the homochiral gauche-gauche dimer is predicted to be the most stable ethanol dimer conformation. The harmonic MP2 predictions are corroborated by perturbative anharmonicity contributions and CCSD(T) energies. Thus, a consistent picture of the subtle hydrogen bond energetics and vibrational dynamics of the ethanol dimer is starting to emerge for the first time.
