Excess molar enthalpies for [emim][BF4] + pyrrolidin-2-one or 1-methyl pyrrolidin-2-one + pyridine or water mixtures

• The HE   and HijkE data have been measured over entire composition range at 298.15 K.
• The observed data have been fitted to Redlich–Kister equation.
• The observed data have been analyzed in terms of Graph and PFP theories.
• The values calculated by Graph theory compare well with experimental values.

Excess molar enthalpies, HijkE of ternary 1-ethyl-3-methylimidazolium tetrafluoroborate (i) + Pyrrolidin-2-one (j) + Pyridine or Water (k); 1-ethyl-3-methylimidazolium tetrafluoroborate (i) 1-methyl pyrrolidin-2-one (j) + Pyridine or Water (k) and HE of Pyrrolidin-2-one (i) + Pyridine or Water (j); 1-methyl pyrrolidin-2-one (i) + Pyridine (j); 1-ethyl-3-methylimidazolium tetrafluoroborate (i) + Water (j) mixtures have been measured over entire mole fraction range at 298.15 K. The HijkE value for 1-ethyl-3-methylimidazolium tetrafluoroborate (i) + Pyrrolidin-2-one (j) + Water (k); 1-ethyl-3-methylimidazolium tetrafluoroborate (i) + 1-methyl pyrrolidin-2-one (j) + Pyridine or Water (k) are positive over whole range of composition and for 1-ethyl-3-methylimidazolium tetrafluoroborate (i) + Pyrrolidin-2-one (j) + Pyridine (k  ) mixture, the sign of HijkE values varies with change in composition of the components. The observed data have been analyzed in terms of (i) Graph; and (ii) Prigogine–Flory–Patterson (PFP) theories. Results indicate that HE   and HijkE values obtained by Graph theory are in good agreement with experimental data. The PFP theory correctly predict sign as well as magnitude of HE   values for the binary mixtures. However, theory fails to predict the sign of HijkE values for the ternary mixtures.