Properties of protic ionic liquids composed of N-alkyl (= hexyl, octyl and 2-ethylhexyl) ethylenediaminum cations with trifluoromethanesulfonate and trifluoroacetate anion

Abstract

Protic ionic liquids (PILs) composed of N-alkyl (=hexyl, octyl and 2-ethylhexyl) ethylenediaminum cation with trifluoromethanesulfonate (TFS) or trifluoroacetate (TFA) anion such as HOct(TFA), HEtHex(TFA), HHex(TFS), HOct(TFS) and HEtHex (TFS) were newly synthesized and HHex(TFA) was synthesized according to the method from a literature. Among them, HHex(TFA), HEtHex(TFA) and HEtHex (TFS) are room temperature ionic liquids. The PILs with TFS exhibit more thermostable than the PILs with TFA and their decomposition temperatures are about 250°C and 150°C, respectively. The physical properties such as density, viscosity and electric conductivity of the PILs were studied in the temperature range of (293.15 to 353.15) K. Temperature dependence of the viscosity and the conductivity was discussed using the Arrhenius equation. The relationship between the molar conductivity and the fluidity was described on the basis of the Walden rule. The results show that the PILs with TFS have a larger ionic mobility compared to the PILs with TFA.