Physical-chemical properties of chiral ionic liquids derived from the phenylethylamine enantiomers

Sixteen imidazolium based chiral ionic liquids (CILs) containing Br- and BE4- anions, derived from both enantiomers of phenylethylamine, were synthesized. The imidazole ring was constructed through a condensation reaction of formaldehyde, glyoxal and ammonium hydroxide in aqueous media resulting in a simple, versatile and environmentally friendly protocol. The CILs were synthesized with propyl, butyl, pentyl or hexyl alkyl substituents, which provoke a change of the physicochemical properties that were evaluated (glass transition temperature, thermal stability, optical rotation, ionic conductivity, electrochemical window and toxicity). The 1-alkyl-3(1-phenylethyl) imidazolium tetrafluoroborate ([C-n peim]BF4) family showed good thermal stability, large electrochemical window, low toxicity at moderate concentrations, and adequate viscosity. Therefore, these CILs are a good candidates to be used in asymmetric reactions and may be a viable alternative to organic solvents. (C) 2017 Elsevier B.V. All rights reserved.