Orientational Effects and Random Mixing in 1-Alkanol + Nitrile Mixtures

Abstract

1-Alkanol + alkanenitrile or + benzonitrile systems have been investigated by means of the molar excess functions—enthalpies (HmE), isobaric heat capacities (Cp,mE), volumes (VmE), and entropies—and using the Flory model and the concentration–concentration structure factor (SCC(0)) formalism. From the analysis of the experimental data available in the literature, it is concluded that interactions are mainly of dipolar type. In addition, large HmE values contrast with rather low VmE values, indicating the existence of strong structural effects. HmE measurements have been used to evaluate the enthalpy of the hydroxyl–nitrile interactions (ΔHOH–CN). They are stronger in methanol systems and become weaker when the alcohol size increases. In solutions with a given short chain 1-alkanol (up to 1-butanol), the replacement of ethanenitrile by butanenitrile weakens the mentioned interactions. Application of the Flory model shows that orientational effects exist in methanol or 1-nonanol, or 1-decanol + ethanenitrile mixtures. In the former solution, this is due to the existence of interactions between unlike molecules. For mixtures including 1-nonanol or 1-decanol, the systems at 298.15 K are close to their UCST (upper critical solution temperature), and interactions between like molecules are dominant. Orientational effects also are encountered in methanol or ethanol + butanenitrile mixtures because self-association of the alcohol plays a more important role. Aromaticity effect seems to enhance orientational effects. For the remainder of the systems under consideration, the random mixing hypothesis is attained to a rather large extent. Results from the application of the SCC(0) formalism show that homocoordination is the dominant trend in the investigated solutions, and are consistent with those obtained from the Flory model.