In the footsteps of August Michaelis: Syntheses and Thermodynamics of Extremely Low-Volatile Ionic Liquids
Dzmitry H Zaitsau1, Anke Topp2, Antje Siegesmund2
1Department of Physical Chemistry and Faculty of Interdisciplinary Research, Competence Centre CALOR, University of Rostock, Dr.-Lorenz-Weg 2, 18059, Rostock, Germany.
Abstract:
A series of nine different known ionic liquids or low melting salts was synthesised and purified. They are composed of the [NTf2 ]- (bis(trifluoromethane)sulfonimide), [OTf]- (trifluoro-methane-sulfonate), or [B(CN)4 ]- (tetracyanidoborate) anion and [Ph4 P]+ (tetraphenylphosphonium), [Ph3 BzP]+ (triphenylbenzyl phosphonium), [n Bu4 P]+ (tetra-n butylphosphonium), [n BuPh3 P]+ (tri-phenyl-n butylphosphonium), [n Bu4 N]+ (tetra-n butylammonium), or the [PPN]+ (bis(triphenylphosphine)iminium) cation. Precise vapour pressure data and enthalpies of vaporisation were measured using the Quartz Crystal Microbalance (QCM) method and evaluated. Structure-property relations are established using the obtained data as well as literature known data of ILs with alkyl-substituted imidazolium cations. It turns out that ILs with the tetracyanidoborate anion have even higher values of the enthalpy of vaporisation than those with the common [NTf2 ]- or [OTf]- anion and therefore are even less volatile.
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