Excess molar volumes VE, excess molar enthalpies HE, and speeds of sound u for 1-methyl pyrrolidin-2-one (1) + water or propan-1-ol or propan-2-ol (2) binary mixtures have been measured over the entire composition range (at 308.15 K) using a dilatometer, calorimeter and interferometer. Speeds of sound data, u, of (1 + 2) binary mixtures have been utilized to determine excess isentropic compressibilities, \documentclass[12pt]{minimal}
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\begin{document}$$ \kappa_{S}^{\text{E}} $$\end{document}. The observed VE, HE and \documentclass[12pt]{minimal}
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\begin{document}$$ \kappa_{S}^{\text{E}} $$\end{document} data have been analyzed in terms of (1) Graph theory (which involves the topology of the constituents of mixture), and (2) the Prigogine–Flory–Patterson theory. Analysis of VE data in terms of Graph theory suggests that 1-methyl pyrrolidin-2-one, water, propan-1-ol, and propan-2-ol exist as associated molecular entities. IR studies lend additional support to the proposed molecular entities in (1 + 2) mixtures. It has been observed that VE, HE and \documentclass[12pt]{minimal}
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\begin{document}$$ \kappa_{S}^{\text{E}} $$\end{document} values predicted by Graph theory compare well with their corresponding experimental values.