Molecular interactions in formamide plus isomeric butanols: An ultrasonic and volumetric study

Densities, rho, ultrasonic speeds, u and viscosities, eta of the binary mixtures of formamide ( FA) with 1-butanol, 2-methyl-1-propanol, and 2-methyl-2-propanol, including those of pure liquids, were measured over the whole composition range at 35degreesC. Using the experimental values of rho, u and eta, the deviations in isentropic compressibility, Deltakappa(s), excess volume, V-E, viscosity, Deltaeta, and excess Gibbs energy of activation of viscous flow, G*(E), were calculated from the linear dependence of these parameters on composition of mixtures. The apparent molar isentropic compressibility, K-phi,K-2 and apparent molar volume, V-phi,V-2 of alcohols in FA were also calculated. The variations of these parameters with composition are discussed from the point of view of intermolecular interactions in these mixtures. The V-E data have also been analyzed using Prigogine-Flory-Patterson theory. An analysis of each of the three contributions, viz., interactional, free volume, and P* effect to V-E shows that P*, the internal pressure parameter of the theory, plays a dominant role in deciding the sign and magnitude of V-E.