Thermodynamics of mixtures containing a very strongly polar compound. 12. Systems with nitrobenzene or 1-nitroalkane and hydrocarbons or 1-alkanols

TL;DR

This study investigates the thermophysical properties and molecular interactions in mixtures of nitrobenzene, 1-nitroalkanes, hydrocarbons, and 1-alkanols, revealing how molecular size and polarity influence their behavior.

Contribution

It provides new interaction parameters and insights into dipolar interactions and molecular structure effects in these complex mixtures.

Findings

Dipolar interactions weaken with increasing size of 1-nitroalkanes.

Nitrobenzene exhibits stronger dipolar interactions than smaller 1-nitroalkanes.

Adding 1-alkanols enhances dipolar polarization and affects molecular structure.

Abstract

Mixtures involving nitrobenzene and hydrocarbons, or 1-alkanols and 1-nitroalkane, or nitrobenzene have been investigated based on a whole set of thermophysical properties available in the literature: excess molar functions (enthalpies, entropies, isobaric heat capacities, and volumes), vapour-liquid and liquid-liquid equilibria, permittivities or dynamic viscosities. In addition, the mixtures have been studied by means of the DISQUAC, ERAS, and UNIFAC models, and the concentration-concentration structure factor. The corresponding DISQUAC and ERAS interaction parameters are reported. In alkane mixtures, dipolar interactions between 1-nitroalkane molecules are weakened when the size of the polar compound increases, accordingly with the relative variation of their effective dipolar moment. Dipolar interactions are stronger in nitrobenzene solutions than in those containing the smaller 1-nitropropane, although both nitroalkanes have very similar effective dipole moment (aromaticity effect). Systems with 1-alkanols are characterized by dipolar interactions between like molecules which sharply increases when the alkanol size increases. Simultaneously, interactions between unlike molecules become weaker, as the OH group is then more sterically hindered. Interactions between unlike molecules are stronger in systems with nitromethane than in nitrobenzene solutions. The replacement of nitromethane by nitroethane in systems with a given 1-alkanol leads to strengthen those effects related with the alcohol self-association. Permittivity data and results on Kirkwood correlation factors show that the addition of 1-alkanol to a nitroalkane leads to cooperative effects, which increase the dipolar polarization of the solution, in such way that the destruction of the existing structure in pure liquids is partially counterbalanced. This effect is less important when longer 1-alkanols are involved.