The activity coefficients at infinite dilution (gamma(infinity)(13)) for 64 solutes including water in two new ammonium-based ionic liquids (ILs), the dimethyldodecylphenoxyethylammonium bis{(trifluoromethyl)sulfonyl} imide, [N-1,N-1,N-12,N-2Oph][NTf2] and dimethyldodecylphenoxyethylammonium dicyanamide, [N-1,N-1,N-12,N-2Oph][DCA] were determined by gas-liquid chromatography at six temperatures in range of (318.15-368.15) K and (328.15-378.15) K for [N-1,N-1,N-12,N-2Oph][NTf2] and [N-1,N-1,N-12,N-2Oph][DCA], respectively. The thermodynamic functions, the limiting partial molar excess Gibbs energy, enthalpy and entropy were calculated. The values of selectivity and capacity for water/butan-1-ol separation problem were calculated from gamma(infinity)(13) and compared to literature values for ammonium-based or other selected ionic liquids for the same separation problem. On the bases of the results, the intermolecular interactions of the chosen ILs and solutes were discussed. The data presented here shows that [N-1,N-1,N-12,N-2Oph][NTf2] reveals attractive selectivity with low capacity and [N-1,N-1,N-12,N-2Oph][DCA] shows attractive capacity with low selectivity in the water/butan-1-ol separation. (C) 2018 Elsevier B.V. All rights reserved.