Synthesis and characterization of novel chiral ionic liquids and investigation of their enantiomeric recognition properties

David K. Bwambok, Hadi Marwani, Vivian E. Fernand, Sayo O. Fakayode, Mark Lowry, Ioan Negulescu, Robert M. Strongin, Isiah M. Warner

Research output: Contribution to journalJournal articlepeer-review

70 Scopus citations

Abstract

We report the synthesis and characterization of amino acid ester based chiral ionic liquids, derived from L- and D-alanine tert butyl ester chloride. The synthesis was accomplished via an anion metathesis reaction between commercially available L-and D-alanine tert butyl ester chloride using a variety of counterions such as lithium bis (trifluoromethane) sulfonimide, silver nitrate, silver lactate, and silver tetrafluoroborate. Both enantiomeric forms were obtained as confirmed by bands of opposite sign in the circular dichroism spectra. The L- and D-alanine tert butyl ester bis (trifluoromethane) sulfonimide were obtained as liquids at room temperature and intriguingly exhibited the highest thermal stability (up to 263°C). In addition, the ionic liquids demonstrated enantiomeric recognition ability as evidenced by splitting of racemic Mosher's sodium salt signal using a liquid state 19F nuclear magnetic resonance (NMR) and fluorescence spectroscopy. The L- and D-alanine tert butyl ester chloride resulted in solid salts with nitrate, lactate, and tetrafluoroborate anions. This illustrates the previously observed tunability of ionic liquid synthesis, resulting in ionic liquids of varying properties as a function of varying the anion.

Original languageEnglish
Pages (from-to)151-158
Number of pages8
JournalChirality
Volume20
Issue number2
DOIs
StatePublished - Feb 2008
Externally publishedYes

Keywords

  • Chiral ionic liquids
  • Chiral recognition
  • Chiral selectors
  • Synthesis

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