Partial molar volumes and isentropic compressibilities of mixtures of γ-butyrolactam (n= 5) with higher alkanols

Abstract

Ultrasonic speed, u, and excess volume, V^E, measurements have been made for mixtures of pyrrolidin-2-one +n-alkanol (C₆–C₁₀) over the entire composition range at 303.15 K. V^E values are negative for pyrrolidin-2-one + hexanol, S-shaped for heptanol and completely positive for rest of the mixtures and increase in the order hexanol < heptanol < octanol < nonanol < decanol. The V^E results have been used to calculate the excess partial molar volumes of the components and have also been analysed using Prigogine–Flory–Patterson theory which divides V^E into three contributions viz. the interactional, free volume and P* effects. It has been found that the dominant role is played by the interactional term which is the main parameter for deciding the sign and magnitude of excess volumes for pyrrolidin-2-one + alkanol (C₆–C₁₀) mixtures.

The estimates of the isentropic compressibilities k_s and of its excess counterpart, k_s^E have been computed from density values (calculated from excess volumes) in combination with ultrasonic speed data. The magnitude of k_s^E values are negative for all the systems over the complete mole fraction range and increase in the order hexanol < heptanol < octanol < nonanol < decanol. The apparent molar isentropic compressibilities ϕ_k,s have been derived and its limiting value K° at an infinite dilution has been estimated.