Data on the liquid-liquid equihbrium (LLE) for the systems water + [2-HEA][Pr], [2-HEA][Bu], and [2-HEA][Pe] + 1-pentanol were determined at 293.15, 313.15, and 333.15 K and atmospheric pressure. Phase diagrams of the ternary systems were determined using the turbidimetric titration method and the tie-lines were quantified using the gravimetric method. Othmer-Tobias correlation confirms the quality of the experimental LLE data (R-2 > 0.95). The NRTL (nonrandom two-liquid) and UNIQUAC (universal quasichemical) models were used to predict LLE data, with satisfactory results of root-mean-square deviations (RMSD) of each model at 1.55 and 1.90%, respectively.