Hydration and sodium-ion binding of trifluoroacetate in aqueous solution

► Study of hydration and sodium-ion binding of trifluoroacetate and acetate. ► Carboxylate group hydrated by ~5-6 water molecules for both anions. ► Fragile hydration shell around -CH3 and -CF3 with ~6 respectively ~15 H2O at c→0. ► Weak doubly solvent-separated ion pairs of trifluoroacetate and acetate with Na+.