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Siegel der Universität
Department für Chemie - Arbeitsgruppe Prof. Strey

Mikroemulsionen als Reaktionsmedium für die Organokatalyse durch N-Heterocyclische Carbene

Tim Schreiner, 2014


In organic synthesis N-heterocyclic carbenes (NHCs) as organocatalysts have an enormous potential. Based on their hydrophobic character, the range of application is mostly limited to hydrophobic reaction partners and non-polar solvents. Microemulsions circumvent this limitation due to their ability to provide a mix of polar and non-polar solvents at the nanoscale, featuring at the same time a huge internal interface leading to higher reaction rates. In this work the remarkable advantages of NHCs and microemulsions are combined for polymerisation reactions of hydrophilic aldehydes. For this purpose the influence of formaldehyde(aq) as well as the NHC 1,3,4-triphenyl-4,5-dihydro-1H-1,2,4-triazol-5-ylidene on the phase behavior was studied. The reaction took place in the three phase region of the modified microemulsion. Investigations by nuclear magnetic resonance spectroscopy (NMR) revealed the inhibiting influence of methanol and oxygen on the reaction progress. Further reactions with more stable carbenes confirmed these results. To optimize the reaction system, formaldehyde(aq) was replaced by the dialdehyde glyoxal(aq). During the improved reaction a change in the phase states occurred, which indicates a possible, yet unkown, product formation.