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Keywords:

  • ionic liquid;
  • ion hydration;
  • nuclear magnetic resonance (NMR) relaxation;
  • kosmotropicity;
  • enzyme;
  • enantioselectivity;
  • Hofmeister series

Abstract

The nuclear magnetic relaxations of water in ionic-liquid (IL) solutions were examined at various IL concentrations in order to better understand their hydration behaviors (in terms of nuclear magnetic resonance (NMR) B′-coefficients). From these B′-values of ILs, the individual ion's B′-coefficients were further calculated based on the additivity. These coefficients represent the hydration behavior (‘kosmotropicity’) of ILs in aqueous solutions. Using these data, a linear correlation was found between enzyme enantioselectivity in aqueous solution and the δ′ parameter (difference in NMR B′-coefficients of anion and cation). In general, high enzyme enantiomeric ratios (E) could be achieved in solutions of ILs with high δ′ values. Copyright © 2007 Society of Chemical Industry