Polarity of pure ionic liquids and at the phase boundary with inorganic solid catalysts

• Applicant: Professor Dr. Stefan Spange
• Subject Area: Preparatory and Physical Chemistry of Polymers
• Term: from 2006 to 2015
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 28750435

The polarity and catalytic reactivity at the interface of inorganic solid acids (silica gels, aluminosilicates, aluminium oxide) with ionic liquids (RTIL - room temperature ionic liquids) will be studied with the aid of soIvatochromic probes and with the kinetics of model reactions. The most important goal is the combination of the advantages of heterogeneous catalysis with the chemistry of ionic liquids, in order to design new reaction media.In order to determine the local polarities of ionic liquids at interfaces, various solvatochromic dyes will be measured in particle suspensions of ionic liquids using UV/visible spectroscopy. These dyes respond preferentially to the acidity (hydrogen bond donating ability, HBA) ¿, basicity (hydrogen bond acceptor ability) ß, and dipolarity/polarisability ¿* respectively. The individual parameters ¿, ß and ¿* will be evaluated using multiple correlation analysis. First the conceptual question must be discussed, on how the individual parameters ¿, ß and ¿* are to be evaluated for pure ionic liquids. It is intended to develop an HBA-scale for anions of ionic liquids. This is the central point of the first part of the project.In the second part the aim is the conceptual development of ionic liquids, adsorbed on solid acid particle surfaces, which should show no RTIL properties in the unadsorbed form. Thus non-symmetrically substituted imidazolium, pyridinium, and tetraalkylammonium salts will be used, where the strength of the anion-solid surface interaction will be set selectively, in order to reduce the cation-anion interactions. As a model reaction for the quantification of surface properties, the transfer of hydride ions to carbenium ions will be used, where the rate constants of the reaction will be determined, and will be correlated to the polarity parameters according to the best available technology.

• DFG Programme: Priority Programmes
• Subproject of: SPP 1191: Ionic Liquids