Thermodynamics Research Center / ThermoML | Journal of Chemical and Engineering Data

ABSTRACT

The distribution of picrate anions in various ionic liquid (IL)/water biphasic systems was investigated at 298.2 K. The ILs were 1-butyl-3-methylimidazolium hexafluorophosphate, 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)amide, 1-hexyl-3-methylimidazolium hexafluorophosphate, 1-hexyl-3-methylimidazolium bis(trifluoromethanesulfonyl)amide, 1-methyl-3-octylimidazolium tetrafluoroborate, 1-methyl-3-octylimidazolium hexafluorophosphate, 1-methyl-3-octylimidazolium bis(trifluoromethanesulfonyl)amide, 1-methyl-3-octylimidazolium bis(pentafluoroethanesulfonyl)amide, 1-butyl-2,3-dimethylimidazolium bis(trifluoromethanesulfonyl)amide, 1-butyl-1-methylpyrrolidinium bis(trifluoromethanesulfonyl)amide, methyltrioctylammonium bis(trifluoromethanesulfonyl)amide, 1-butylimidazolium bis(trifluoromethanesulfonyl)amide, and 1-butylpyrrolidinium bis(trifluoromethanesulfonyl)amide. The distribution ratios in dilute conditions (Ddeg ) and the aqueous solubilities of the ILs (square root of the solubility product, Ksp1/2) were determined. The extractability of the picrate anion generally increases with increasing hydrophobicity of the IL cation (C+) and increasing hydrophilicity of the IL anion (A ). For the ILs with different C+ but the same A , the log Ddeg vs log Ksp1/2 plot generally gives a linear relationship with a slope of -1; when the ILs have similar Ksp1/2 values, the Ddeg value decreases in the C+ order, protic cations 1,3-dialkylimidazolium cations greater than other cations. For the ILs comprising different A but the same C+, the log Ddeg versus log Ksp1/2 plot is close to a linear line with a slope of 1. These regularities can be explained on the basis of the extraction mechanism including both the ion pair extraction with C+ and the ion exchange with A .