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

TL;DR

This study measures densities, excess molar volumes, and enthalpies of (2-propanol + glyme) mixtures across various glyme chain lengths, applying the Flory model to understand structural and interaction effects in these liquids.

Contribution

It provides new experimental data on thermodynamic properties of glyme-alcohol mixtures and applies the Flory model to interpret molecular interactions and structural effects.

Findings

Excess molar volumes are small or negative, indicating structural effects dominate.

Strong alkanol-ether interactions do not significantly affect excess molar enthalpy.

The Flory model reveals weak orientational effects in glyme mixtures, stronger in di-n-propyl ether.

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.