Volume and compressibility of mixtures of γ-butyrolactam (n = 5) with nitro-compounds

Excess volume and ultrasonic velocity measurements have been carried out for nitromethane (NM), nitroethane (NE), 1-nitropropane (1-NP), 2-nitropropane (2-NP) and nitrobenzene (NB) in γ-butyrolactam (n=5), i.e. pyrrolidin-2-one (PY) at 303.15 K over the entire composition range. The VE values are negative for PY+nitroalkanes expect for NM which exhibits S-shaped behaviour. A very small VE is observed in PY+NB. Using ultrasonic velocity and excess volume data, molar isentropic compressibility KS and excess isentropic compressibility KSE have been computed. The results have been analysed in the following sequence. (1) Quantitative estimation of different contributions, viz. interactional, free volume and P∗ effect to VE using Prigogine–Flory–Patterson (PFP) theory; (2) the calculation of partial molar volumes, apparent molar compressibility and their excess values to gain insight into solute–solvent interactions.