Orientational effects in mixtures of organic carbonates with alkanes or 1-alkanols

TL;DR

This study investigates the molecular interactions and structural properties of mixtures involving organic carbonates, alkanes, and 1-alkanols using various thermodynamic and modeling approaches, revealing the influence of dipolar interactions and molecular size.

Contribution

It provides a comprehensive analysis of orientational effects and interaction energies in carbonate-alkane and carbonate-alkanol mixtures using experimental data and theoretical models.

Findings

Dipolar interactions weaken in the order PC > DMC > DEC.

Orientational effects are strongest in DEC mixtures, especially with methanol or ethanol.

Interactions are influenced by group size and dipole moment, not just dipole strength.

Abstract

Interactions and structure of organic carbonate + alkane, and 1-alkanol + organic carbonate mixtures have been investigated by means of a set of molar excess functions: enthalpies, volumes, isobaric heat capacities, or entropies; and considering internal pressure, liquid-liquid equilibria or permittivity data. In addition, the mentioned systems have been studied using the Flory model and the concentration-concentration structure factor formalism. The mixtures under consideration are characterized by dipolar interactions and by homocoordination (that is, by interactions between like molecules). In systems with a given solvent, dipolar interactions are weakened in the order: propylene carbonate (PC) > dimethyl carbonate (DMC) > diethyl carbonate (DEC). Comparison of mixtures containing DMC or DEC with those involving 2-propanone or 3-pentanone shows that dipolar interactions are not determined merely by values of the dipole moment, but they also depend on the group size. The enthalpies of the alkanol-carbonate interactions have been evaluated from calorimetric data. They are stronger in DMC solutions and become weaker when the alcohol size increases in mixtures with a given carbonate. Application of the Flory model to 43 systems of the type 1-alkanol + carbonate provides a mean relative standard deviation for excess molar enthalpy equal to 0.107. Results reveal that orientational effects decrease in the order DEC > PC > DMC. Orientational effects are particularly relevant in methanol or ethanol + DEC mixtures. Interestingly, the mentioned effects are weaker in 1-alkanol + DMC mixtures than in DMC + alkane systems. A similar trend is observed in DEC solutions when the considered alcohol is longer than ethanol.