Density and excess molar enthalpy of (2-propanol + glyme) liquid mixtures. Application of the Flory model

Abstract

For glymes of general formula CH3O(CH2CH2O)uCH3, with u = 1, 2, 3, 4, the densities of the (2-propanol + glyme) systems at temperatures ranging from (293.15 to 303.15) K and at pressure 0.1 MPa were determined using a DSA 5000 densimeter (from Anton Paar). The corresponding excess molar volumes were calculated from these density measurements. In addition, excess molar enthalpies at 298.15 K and 0.1 MPa were measured using a Tian-Calvet micro-calorimeter. The results show that alkanol–ether interactions are strong but do not contribute significantly to the excess molar enthalpy, as the values are large and positive, and comparable to those of (glyme + n-heptane) systems. The excess molar volumes are small or even negative (in the case of the mixture with u = 4), indicating that they are mainly governed by structural effects. Mixtures with 1-propanol or 2-propanol behave similarly, although interactions between unlike molecules become slightly stronger when 1-propanol is involved. On the other hand, effects related to alcohol self-association play a decisive role in the thermodynamic properties when glymes are replaced by di-n-propyl ether. This is supported by the application of the Flory model, which shows that orientational effects are weak in the studied glyme-containing mixtures but become significantly stronger when di-n-propyl ether is considered.