Distribution of a Monovalent Anion in Various Ionic Liquid/Water Biphasic Systems: Relationship of the Distribution Ratio of Picrate Ions with the Aqueous Solubility of Ionic Liquids

作者：Watanabe Yuta; Katsuta Shoichi^*

来源：Journal of Chemical and Engineering Data, 2014, 59(3): 696-701.

DOI：10.1021/je400726y

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-octylimidazobum 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 (D-o) and the aqueous solubilities of the ILs (square root of the solubility product, K-sp(1/2)) 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 D-o vs log K-sp(1/2) plot generally gives a linear relationship with a slope of -1; when the ILs have similar K-sp(1/2) values, the D-o value decreases in the C+ order, protic cations %26gt;%26gt; 1,3-dialkylimidazolium cations %26gt; other cations. For the ILs comprising different A(-) but the same C+, the log D-o versus log K-sp(1/2) 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(-).

• 出版日期2014-3