Ultrasonic and viscometric studies of molecular interactions in binary mixtures of formamide with ethanol, 1-propanol, 1,2-ethanediol and 1,2-propanediol at different temperatures

The ultrasonic speeds, u and viscosities, eta of binary mixtures of formamide (FA) with ethanol, 1-propanol, 1,2-ethanediol, and 1,2-proparrediol, including those of pure liquids, over the entire composition range were measured at 293.15, 298.15, 303.15, 308.15, 313.15, and 318.15 K. From the experimental values of u and eta, the deviations in isentropic compressibility, Delta k(s), in ultrasonic speed, Delta u, and in viscosity, Delta eta were calculated. The variation of these parameters with composition and temperature of the mixtures are discussed in terms of molecular interaction in these mixtures. The observed trends in Delta k(s) values indicate the presence of specific interactions between FA and alkanol molecules. The Delta k(s) values follow the order: ethanol < 1-propanol < 1,2-propanediol < 1,2-ethanediol. It is observed that the Delta k(s) values depend upon the number of hydroxyl groups and alkyl chain length in these alkanol molecules. Furthermore, the free energies, Delta G*, enthalpies, Delta H* and entropies, Delta S* of activation of viscous flow have also been obtained by using Eyring viscosity equation and their dependence on composition of the mixtures have been discussed. (c) 2008 Elsevier B.V. All rights reserved.