Excess volumes and isentropic compressibilities of pyrrolidin-2-one–alkanol (C1–C5) binary mixtures

The velocity of sound, u, and excess volume, VE, have been determined at 303.15 K for binary mixtures of pyrrolidin-2-one +n-alkanol (C1–C5) over the whole composition range. The isentropic compressibilities Ks and their excess values KEs have been estimated and shown to be negative for all systems over the entire composition range and to vary in the order methanol < ethanol < propanol < butanol < pentanol. The VE results have been used to estimate the excess partial molar volumes of the components and have also been analysed in the light of Prigogine–Flory–Patterson theory. An analysis of each of the three contributions viz. interactional, free volume and P* to VE, shows that the interactional contribution is positive for all systems except methanol which has a small negative interactional contribution. The free volume effect and P* contribution are negative for all the mixtures. To explore the nature of the interactions, various thermodynamic parameters i.e. free volume, Vf, solvation number, Sn, Wada's constant W, and Rao's constant, R, have been derived from the u and ρ data. The behaviour of these parameters indicates the absence of any complex formation in the mixtures studied.