Physicochemical and acid-base properties of a series of 2-hydroxyethylammonium-based protic ionic liquids.
Physicochemical properties such as a thermal behavior, ionic conductivity, viscosity and density, and acid-base properties of a new class of 2-hydroxyethylammonium-based protic ionic liquids (PILs) have been investigated. Thirty-six potential PILs were surveyed to find 32 salts with a melting point below 373 K. Among them, [(EtOH)(n)Et((3-n))NH(+)][TFS(-)] (Et, C(2)H(5); n = 0 - 3) and [(EtOH)(2)EtNH(+)][X(-)] (X = TFS, trifluoromethanesulfonate; TFSA, bis(trifluoromethanesulfonyl)amide; NO(3)) were studied in terms of the Walden plots, molar volume and auto-protolysis reaction for effect of the number of 2-hydroxyethyl groups introduced in the cations and for dependence of the anion nature, respectively. With regard to [(EtOH)(n)Et((3-n))NH(+)][TFS(-)] (n = 0 - 3), the ion-ion interactions between cation-anion and cation-cation were enhanced with increasing the number of the 2-hydroxyethyl groups. In addition, the auto-protolysis constant K(s) value for [(EtOH)(2)EtNH(+)][TFSA(-)] is smaller than that for TFS(-) based PIL, indicating that HTFSA behaves as a stronger acid than HTFS in the respective PIL. On the other hand, in [(EtOH)(2)EtNH(+)][NO(3)(-)], the emf jump was rather small, which suggests that the proton of HNO(3) does not easily transfer to (EtOH)(2)EtN in the liquid state.
Department of Chemistry, Faculty of Sciences, Kyushu University, Higashi, Fukuoka, Japan.
Xuedan
X
Song
Ryo
R
Kanzaki
Shin-ichi
S
Ishiguro
Yasuhiro
Y
Umebayashi
D000136:Acid-Base Equilibrium; D002627:Chemistry, Physical; D004553:Electric Conductivity; D052578:Ionic Liquids / Q000737:chemistry*; D000644:Quaternary Ammonium Compounds / Q000737:chemistry*; D013696:Temperature; D014783:Viscosity
D052578:Ionic Liquids; D000644:Quaternary Ammonium Compounds