A combined Raman- and infrared jet study of mixed methanol-water and ethanol-water clusters
A combined Raman- and infrared jet study of mixed methanol-water and ethanol-water clusters Nedic, M.; Wassermann, T. N.; Larsen, R. W. & Suhm, M. A. (2011) Physical Chemistry, Chemical Physics, 13(31) pp. 14050-14063.
Nedic, Marija; Wassermann, Tobias N.; Larsen, Rene Wugt; Suhm, Martin A.
Royal Soc Chemistry
Physical Chemistry, Chemical Physics
Institut für Physikalische Chemie
The vibrational dynamics of vacuum-isolated hydrogen-bonded complexes between water and the two simplest alcohols is characterized at low temperatures by Raman and FTIR spectroscopy. Conformational preferences during adaptive aggregation, relative donor/acceptor strengths, weak secondary hydrogen bonding, tunneling processes in acceptor lone pair switching, and thermodynamic anomalies are elucidated. The ground state tunneling splitting of the methanol-water dimer is predicted to be larger than 2.5 cm(-1). Two types of alcohol-water trimers are identified from the spectra. It is shown that methanol and ethanol are better hydrogen bond donors than water, but even more so better hydrogen bond acceptors. As a consequence, hydrogen bond induced red shifts of OH modes behave non-linearly as a function of composition and the resulting cluster excess quantities correspond nicely to bulk excess enthalpies at room temperature. The effects of weak C-H center dot center dot center dot O hydrogen bonds are quantified in the case of mixed ethanol-water dimers.
Publication of Göttingen University
Funder: DFG [Su121/2, GRK 782]; Danish Research Council