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
19
F 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.