Interactions, Dynamics and Structure in the Ionic Liquid-scCO2 system
Physical Chemistry of Molecules, Liquids and Interfaces, Biophysical Chemistry
Final Report Abstract
The asymmetric hydrogenation of the prochiral substrates atropic acid and tiglic acid was studied as chemical probe to assess the role of CO2 in affecting the enantioselectivity in the ionic liquid/CO2 system. The influence of H2 and CO2 pressure, stirring rate and catalyst/substrate concentration on the enantioselectivity was carefully examined. The H2 concentration in solution was measured by high-pressure NMR spectroscopy and correlated with the observed enantioselectivity. The results demonstrated that the presence of CO2 resulted in higher enantioselectivity for atropic acid, but lower selectivity for tiglic acid. Moreover, it could be confirmed that the increased H2 concentration in IL in the presence of CO2 is not the only factor affecting the enantioselectivity, suggesting the interactions in the IL/CO2 system relative to the pure IL playing an additional important role. The high pressure ROESY studies provided direct evidence and showed that the addition of CO2 does not significantly change the polar network of ILs, but caused a clear rearrangement in the alkyl tails to accommodate CO2 molecules. Moreover, 103Rh NMR measurement showed that cationic and neutral metal complex are immobilized either in polar domain or nonpolar domain in the IL/CO2 system. In summary, the presented results depicted the essential factors controlling the selectivity in catalytic reactions in the IL/CO2 system and enable in future a rational selection of catalysts an ILs for catalysis in this reaction media.
Publications
- Expanded Liquid Phases in Catalysis: Gas-expanded Liquids and Liquid-Supercritical Fluid Biphasic Systems. in: Handbook of Green Chemistry, Vol. 4: Supercritical Solvents, eds.: W. Leitner, P.G.
Jessop), Wiley-VCH 2010, S. 101-187.
U. Hintermair, W. Leitner, P.G. Jessop
(See online at https://dx.doi.org/10.1002/9783527628698.hgc037) - Continous Flow Organometallic Catalysis: New Wind in Old Sails
Chemical Communications, Vol. 47. 2011, pp. 3691-3701.
U. Hintermair, G. Franciò, W. Leitner
(See online at https://dx.doi.org/10.1039/c0cc04958a) - Transition Metal Complexes in Supported Liquid Phase and Supercritical Fluids – A Beneficial Combination for Selective Continuous Flow Catalysis with Integrated Product Separation.
in: New Strategies in Chemical Synthesis and Catalysis (B. Pignatore, Ed.), Wiley-VCH, 2012, pp. 273–296.
U. Hintermair, T. Chinnusamy, W. Leitner
(See online at https://dx.doi.org/10.1002/9783527645824.ch12)
