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Effect of an "ionic liquid" cation, 1-butyl-3-methylimidazolium, on the molecular organization of H2O

TitleEffect of an "ionic liquid" cation, 1-butyl-3-methylimidazolium, on the molecular organization of H2O
Publication TypeJournal Article
Year of Publication2005
AuthorsMiki, K, Westh, P, Nishikawa, K, Koga, Y
JournalJournal of Physical Chemistry B
Volume109
Pagination9014-9019
Date PublishedMay
Type of ArticleArticle
ISBN Number1520-6106
Keywords25-DEGREES-C, ALKANE-MONO-OLS, AQUEOUS-SOLUTIONS, fluctuations, HEXAFLUOROPHOSPHATE, MIXING SCHEMES, PARTIAL MOLAR ENTHALPIES, SOLVENTS, TERT-BUTANOL MIXTURES, WATER SOLUTIONS
Abstract

The excess partial molar enthalpy of 1-propanol (1P), H-1P(E), was measured at 28 ° C in the ternary mixture of 1P-1-butyl-3-methylimidazolium chloride ([bmim]Cl)-H2O in the H2O-rich composition range. From these data we evaluated what we call the 1P-1P enthalpic interaction function, H-1P-1P(E). Its changes induced by addition of (bmim]Cl of the pattern of H-1P-1P(E) were used as a probe to elucidate the effect of [bmim]Cl on the molecular organization of H2O. It was found that the effect of Cl- was not conspicuous within this methodology, and the observed dependence is predominantly due to the hydration of [bmim](+). The changes in the χ(1P)-dependence of H-1P-1P(E) were compared with those brought about by temperature increase, or by the addition of fructose or glycerol. It was found that the effect of [bmim](+) is similar to that of fructose or increased temperature. We speculate that in the H2O-rich composition region a number of H2O molecules are attracted to the delocalized positive charge of the imidazolium ring and the bulk of H2O is influenced in such a manner that the global hydrogen bond probability is reduced.

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