Partition Behavior of Chlorophenols and Nitrophenols between Hydrophobic Ionic Liquids and Water

• Published in: Journal of chemical and engineering data Vol. 56; no. 11; pp. 4083 - 4089
• Main Authors: Katsuta, Shoichi, Nakamura, Ko-ichi, Kudo, Yoshihiro, Takeda, Yasuyuki, Kato, Hisashi
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 10.11.2011
• Subjects: Chemistry; Exact sciences and technology; General and physical chemistry; Solutions; Water; Nitro compound; Molecular interaction; Partition coefficient; Halophenols; Ionic liquid
• ISSN: 0021-9568; 1520-5134
• DOI: 10.1021/je200506p

The partition of various chlorinated and nitrated phenols between hydrophobic ionic liquids and aqueous solutions of different pH values was investigated at 298.2 K. Ionic liquids used are 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)amide ([BMIm][NTf2]), 1-butyl-1-methylpyrrolidinium bis(trifluoromethanesulfonyl)amide ([BMPyr][NTf2]), 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIm][PF6]), 1-methyl-3-octylimidazolium bis(trifluoromethanesulfonyl)amide ([OMIm][NTf2]), and 1-methyl-3-octylimidazolium tetrafluoroborate ([OMIm][BF4]). Partition coefficients (P IL/W) of the electrically neutral form (ArOH) and the dissociated anionic form (ArO–) were determined. For a given phenol, the P IL/W(ArOH) value in the ionic liquid/water system is generally independent of the kind of the ionic liquid and smaller than that in the 1-octanol/water system. Exceptionally, the P IL/W(ArOH) value in the [OMIm][BF4]/water system is larger than those in the other ionic liquid/water systems and comparable to or greater than that in the 1-octanol/water system. The interaction energies of the ionic liquids with the phenolic hydroxyl group were evaluated. It is shown from the dependence of the interaction energy on the acid-dissociation constant of the phenol that the ionic liquid behaves as both an electron-pair donor and an acceptor like water rather than 1-octanol. The P IL/W(ArO–) value depends largely on the kind of ionic liquid, showing that an ionic liquid formed by a more hydrophobic cation and a more hydrophilic anion has a higher extractability for the phenolate anions. The substituent effects on P IL/W(ArO–) are also different from those on P IL/W(ArOH).