Thermodynamics of Amide + Amine Mixtures. 2. Volumetric, Speed of Sound and Refractive Index Data for N,N-Dimethylacetamide +N-Propylpropan-1-Amine, +N-Butylbutan-1-Amine, +Butan-1-Amine, or +Hexan-1-Amine Systems at Several Temperatures

TL;DR

This study measures and analyzes the volumetric, acoustic, and refractive properties of specific amide-amine mixtures at various temperatures to understand their molecular interactions and structural effects.

Contribution

It provides new experimental data and insights into amide-amine interactions, including excess thermodynamic properties and the application of the PFP model to these systems.

Findings

Amide-amine interactions are characterized by negative or low positive excess molar volumes.

Linear primary amines show more significant amide-amine interaction breaking than secondary amines.

Dispersive interactions are similar in DPA and HxA systems, with differences mainly in dipolar character.

Abstract

Data on density, $\rho$, speed of sound, $c$, and refractive index, $n_{\text{D}}$, of binary systems containing N,N-dimethylacetamide (DMA) + N-propylpropan-1-amine (DPA) or + butan-1-amine (BA) at 293.15 K, 298.15 K and 303.15 K, and + N-butylbutan-1-amine (DBA) or + hexan-1-amine (HxA) at 298.15 K are reported. A densimeter and sound analyzer Anton Paar DSA 5000 has been used for the measurement of $\rho$ and $c$, whereas $n_{\text{D}}$ values have been obtained by means of a refractometer RFM970 from Bellingham+Stanley. Also, values of excess molar volumes, $V_{\text{m}}^{\text{E}}$, excess isentropic compressibilities, $\kappa_S^{\text{E}}$, excess speeds of sound, $c^{\text{E}}$, excess isobaric thermal expansion coefficients, $\alpha_p^{\text{E}}$, and of excess refractive indices, $n_{\text{D}}^{\text{E}}$, have been determined from these data. The investigated systems are characterized by amide-amine interactions and structural effects, as it is shown by their negative or low positive $V_{\text{m}}^{\text{E}}$ values and by the results from the application of the Prigogine-Flory-Patterson (PFP) model. The breaking of amine-amine interactions is more relevant in systems containing linear primary amines than in those with linear secondary amines, and the $V_{\text{m}}^{\text{E}}$ values are lower for the latter systems. Molar refraction has been used to evaluate the dispersive interactions in the mixtures under study, yielding the result that DPA and HxA systems present similar dispersive interactions and mainly differ in their dipolar character. Steric hindrance of the amide group in DMA leads to weaker amide-amine interactions than in the corresponding N,N-dimethylformamide (DMF) + amine systems.