Ionic liquids confined in porous materials are important solvents which allow a simple heterogenization of homogenous liquids. The perdeuterated ionic liquid N-ethylpyridinium-bis(trifluoromethanesulfonyl)amide ([C(2)Py][BTA]-d(10)) was prepared and its bulk phase behavior was studied by differential scanning calorimetry (DSC) and temperature-resolved (2)H and (19)F solid-state NMR spectroscopy. Its bulk properties were compared to [C(2)Py][BTA]-d(10) confined in a mesoporous silica support material as model material usable in SILP catalysts. The line shape analysis of the temperature-dependent NMR spectra of the bulk material reveals two phase transitions, one at 287-289 K (solid II/solid I) and one extending over a temperature range of 298-306 K (solid I/liquid). While the first phase transition is caused by the onset of an intramolecular rotation of the ethyl group of the cation, the second is due to the melting of the ionic liquid. In the bulk material, a hysteresis between the transition temperatures in heating and cooling scans occurs. In confinement, the dynamics of the ionic liquid changes considerably: no hysteresis is observed for [C(2)Py][BTA]-d(10) confined in the mesopores. Instead, only a broad transition from solid II to the liquid state, which spans the temperature range of 215-245 K, is observed. This transition is identified as the result of a broad distribution of molecular environments of the confined ionic liquid, which thus forms an amorphous phase inside the pores. Hence, the behavior of the ionic liquid in confinement is similar to the behavior of non-ionic guest molecules in the mesoporous silica. Finally, it was found that the anion and cation of the ionic liquid exhibit the same dynamic behavior in confinement.

The activation of relatively inert carbon dioxide as a building block for organic products is of interest from both ecological and chemical points of view. One of the few industrially relevant processes using CO 2 is the Kolbe-Schmitt synthesis. Two strategies to obtain the carboxylated product 2,4-dihydroxybenzoic acid from resorcinol are presented: both Dimcarb and hydrogencarbonate-or methylcarbonate-based ionic liquids are employed as reactive solvents in a microwaveassisted reaction. Reaction optimization shows that the ionic liquids are more reactive than Dimcarb. However, Dimcarb offers advantages with regard to ecological aspects, such as the Global Warming and Human Toxicity Potential and the Cumulative Energy Demand, which were assessed as part of the process development.

No abstract

No abstract

Para-hydrogen induced polarization (PHIP) is observed in an organic solvent-free homogeneous catalyst/substrate system using ionic liquids. The hydrogenation reactions are performed employing a Rh-catalyst/ionic liquid system without further organic solvents. The PHIP phenomenon is demonstrated for the ethyl acrylate system. Small amounts of ionic liquids (ILs) containing weakly coordinating anions such as [Tf2N]- act as homogenizing cosolvents for the catalyst in ethyl acrylate, leading to a dramatic activation of the catalytic process and a high PHIP signal enhancement. The achieved enhancement depends strongly on the viscosity of the ethyl acrylate/IL mixture. Furthermore, by deliberate choice of the IL constituents it was possible to design a model system exhibiting both sufficient catalyst solubility and biphasic liquid-liquid behavior. This shows that in ionic liquids PHIP enhancements followed by a fast quantitative removal of the para-hydrogenated product from the catalyst phase is in principle possible. The possible PHIP enhancement factors will depend strongly on the design of a suitable hydrogenation reactor.