[Zurück]

M. López Pastor, M.J. Ayora-Cañada, M. Valcárcel, B. Lendl:
"Association of Methanol and Water in Ionic Liquids Elucidated by Infrared Spectroscopy Using Two-Dimensional Correlation and Multivariate Curve Resolution";
Journal of Physical Chemistry B, 110 (2006), 22; S. 10896 - 10902.

Water and methanol assocns. in ionic liqs. (ILs) were studied by FTIR spectroscopy. Spectra at different concns. of water or methanol in ILs were obtained by online diln. using a flow injection anal. system. Spectral features in the OH stretching region revealed that most of the water and methanol mols. tended to be isolated from each other and to interact with the anion of the IL via H bonding. By two-dimensional correlation spectroscopy, the formation of methanol and water dimers was also detected. Multivariate curve resoln. was used to recover pure spectra and concn. profiles of the different species. Methanol dimers form at concns. >0.8% (wt./wt.) in the three studied ILs, 1-ethyl-3-methylimidazolium tetrafluoroborate (emimBF4), 1-butyl-3-methylimidazolium tetrafluoroborate (bmimBF4), and 1-butyl-3-methylimidazolium hexafluorophosphate (bmimPF6). Self-assocn. of water mols. takes place in emimBF4 and bmimBF4 at a molar ratio similar to that of methanol mols.; however, water dimers cannot be detected in bmimPF6, the most hydrophobic IL studied. No evidence was found that bigger water clusters are formed in these ILs at the studied cosolvent concns.