Molecular association of pentanols in n-heptane II: Viscosities as a function of temperature covering low concentration range

Abstract

Abstract Viscosities of binary mixtures of isomeric pentanols in n-heptane at various mole fractions, F (F = 0.025 to 0.600) have been measured in the low temperature range (T = 233 to 293 K) with an automatic viscometer operating in a closed system. The temperature dependence of viscosity has been found to follow a simple relation, thereby allowing for the calculation of Ev, the activation energy for viscous flow. The latter is very sensitive to changes in molecular associates, especially at low concentrations. The results show that at low concentrations small multimers dominate for both 1-pentanol and 2-pentanol. At high concentrations, while the former may associate to give large linear multimers; the latter may result in the formation of large cyclic multimers with a low dipole moment. For 3-pentanol and tert-pentanol, small multimers are likely to dominate at low concentrations and there is a change in the dominating multimers from a linear type to a cyclic one, with increasing concentration in the limit F