Orientational effects in alkanone, alkanal or dialkyl carbonate + alkane mixtures and in alkanone + alkanone or + dialkyl carbonate systems

TL;DR

This study investigates the molecular interactions and structure of various alkanone, alkanal, dialkyl carbonate, and alkane mixtures using thermodynamic properties and the Flory model, revealing how dipolar interactions and orientational effects vary among systems.

Contribution

It provides new insights into the influence of molecular group size and structure on thermodynamic properties and orientational effects in these liquid mixtures.

Findings

Alkane mixtures exhibit strong dipolar interactions.

Dipolar interactions weaken in the order: aromatic > cyclic > linear.

Orientational effects are similar across ketone and alkanal systems but weaker in dialkyl carbonate mixtures.

Abstract

Interactions and structure of alkanone, or alkanal or dialkyl carbonate + alkane mixtures, or of 2-alkanone+ 2-alkanone, or of ketone + dialkyl carbonate systems have been investigated by means of a set of thermodynamic properties and by the application of the Flory model. The properties considered are excess molar quantities: enthalpies, $H_{\text{m}}^{\text{E}}$, volumes, $V_{\text{m}}^{\text{E}}$, or isobaric heat capacities, $C_{p \text{m}}^{\text{E}}$, and liquid-liquid equilibria. Experimental data show that alkane mixtures are characterized by rather strong dipolar interactions. In the case of systems containing ketones with the same number of C atoms and a given alkane, dipolar interactions become weaker in the sequence: aromatic > cyclic > linear. In addition, the mentioned interactions become also weaker in the order: dialkyl carbonate > linear alkanone > linear alkanal. This is an important result, as carbonates show lower effective dipole moments than the other compounds, and it suggests that the group size may be relevant when evaluating thermodynamic properties of liquid mixtures. Results on $H_{\text{m}}^{\text{E}}$ from the Flory model show that orientational effects (i.e., non-random mixing) are rather similar for systems with linear, cyclic or aromatic ketones or alkanals and alkanes. In contrast, orientational effects become weaker in dialkyl carbonate + alkane mixtures. The behaviour of 2-alkanone + 2-alkanone systems and of mixtures of longer 2-alkanones or cyclohexanone with dialkyl carbonate is close to random mixing. Larger orientational effects are encountered in solutions of carbonates and shorter 2-alkanones.