Molecular interactions in binary mixtures of formamide with 1-butanol, 2-butanol, 1,3-butanediol and 1,4-butanediol at different temperatures: An ultrasonic and viscometric study

The ultrasonic speeds, u and viscosities, η of binary mixtures of formamide (FA) with 1-butanol, 2-butanol, 1,3-butanediol and 1,4-butanediol, including those of pure liquids, over the entire composition range were measured at temperatures 293.15, 298.15, 303.15, 308.15, 313.15 and 318.15 K. From the experimental u and η data, the deviations in isentropic compressibility, Δks, in ultrasonic speed, Δu, and in viscosity, Δη   were calculated. The partial molar compressibilities, K¯m,1 and K¯m,2 of FA and alkanol in the mixtures over the whole composition range and K¯m,1° and K¯m,2° at infinite dilution and excess partial molar compressibilities, K¯m,1E and K¯m,2E, over the whole composition range and K¯m,1°E and K¯m,2°E at infinite dilution were calculated by using two different approaches. The variations of these parameters with composition and temperature of the mixtures are discussed in terms of molecular interaction in these mixtures. It is observed that the FA-alkanol interactions in these mixtures follows the order: 1-butanol < 2-butanol < 1,3-butanediol < 1,4-butanediol. The effect of the number and position of the hydroxyl groups in these alkanol molecules on the molecular interactions in these mixtures is discussed. Furthermore, the free energies, ΔG*, enthalpies, ΔH*, and entropies, ΔS* of activation of viscous flow have also been obtained by using Eyring viscosity equation. The dependence of ΔG*, ΔH* and ΔS* on composition of the mixtures have been discussed.