NMR spectroscopy in studies of new chiral ionic liquids (in English)
Polimery 2011, No 9, 676
Chiral ionic liquids (CILs) were discussed as new potential media for enantioselective organic synthesis, including enantioselective polymer synthesis. NMR spectra of new CILs, whose structures are shown in formulas (I)—(IV), were investigated in detail. In the case of 1H NMR analysis of those compounds two characteristic doublets were observed — diasterotopic protons (AB spin system). In order to precisely determine the spectral position of each proton and carbon, but also to attribute in a detailed way the type of their signals, two-dimensional spectra were obtained. Additionally, 1H NMR and 13C NMR spectra indicated notable differences in the chemical shifts depending on the anion used. Comparing the differences between values of the chemical shifts, the anions, but also the quaternary ammonium salts, depending on the amine used, were ordered according to their increasing shielding capacities.
Key words: quaternary ammonium salt, ionic liquid, chirality, diasterotopic protons, chemical shift