Viscosities and densities for binary mixtures of N-methylpiperazine with methanol, ethanol, n-propanol, iso-propanol, n-butanol and iso-butanol at 293.15, 298.15 and 303.15Â K

Viscosity (η) and density (ρ) values are reported for binary mixtures of N-methylpiperazine (NMP) with methanol, ethanol, n-propanol, iso-propanol, n-butanol and iso-butanol over the entire range of mole fraction at 293.15, 298.15, and 303.15 K and atmospheric pressure. The viscosity deviation (Δη), excess molar volume (VE), and excess Gibbs energy of activation (G*E) have been calculated. These results were fitted with Redlich-Kister type polynomial equation. All the investigated systems exhibit very large positive values of Δη and G*E, and negative values of VE over the whole composition range. The obvious deviations attribute to the strong cross association between the alkanol and NMP molecules through the hydrogen bond of OH⋯N. The temperature has significant effect on Δη and relatively slight effect on VE and G*E. From the experimental data, the thermodynamic functions of activation have been estimated for each binary mixture. The viscosity data have been correlated with several semi-empirical equations. Two-parameter equation of McAllister can give satisfactory results.