Journal of Solution Chemistry

, Volume 38, Issue 6, pp 753–761 | Cite as

Investigation of the Role of Ionic Liquids in Tuning the pK a Values of Some Anionic Indicators

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Abstract

The effect of imidazolium-based ionic liquids, ([C12mim][Cl] and [C8mim][Cl]), on the acid-base equilibria of two sulfonated indicators has been studied. The presence of ILs leads to decreased pK a values because of the stronger electrostatic interaction of cationic ILs with the basic forms of the indicators with more negative charge. The longer alkyl side chain of [C12mim][Cl] compared to [C8mim][Cl] results in stronger hydrophobic interaction of this IL with the basic forms of the dyes leading to a more effective decrease in the pK a values. Also, the transition points and transition intervals of the acid-base titration curves of the indicators were affected by the presence of ILs. It was found that the IL interaction with acid-base indicators also results in sharpening the acid-base titration curves of the indicators. From these observations, it is concluded that the presence of ILs can tune the pK a values of indicators. All the experiments were performed spectrophotometrically and the results were obtained using curve fitting methods.

Keywords

Ionic liquids Imidazolium-based Acid-base equilibrium Titration pKa 
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Copyright information

© Springer Science+Business Media, LLC 2009

Authors and Affiliations

  • A. Safavi
    • 1
  • H. Abdollahi
    • 2
  • N. Maleki
    • 1
  • S. Zeinali
    • 1
  1. 1.Department of Chemistry, College of SciencesShiraz UniversityShirazIran
  2. 2.Department of ChemistryInstitute for Advanced Studies in Basic SciencesZanjanIran

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