Artigo Revisado por pares

Thermodynamics of mixtures containing alkanes

1985; Elsevier BV; Volume: 20; Linguagem: Inglês

10.1016/0378-3812(85)90019-6

ISSN

1879-0224

Autores

Souvik Bhattacharyya, Miguel Costas, D. Patterson, Huu Van Tra,

Tópico(s)

Chemical Thermodynamics and Molecular Structure

Resumo

Binary mixtures of various liquids (components 1) with the n-alkane series (components 2) have given many results for the following excess or mixing functions (XE or ΔX). Of particular interest are: (1) the trend of XE with n; (2) change of XE when the n-Cn are replaced by the corresponding series of highly-branched alkane isomers, and (3) comparison with theoretical predictions. Certain theories, e.g. van der Waals 1, fail in their present form due to neglecting the Prigogine number of external degrees of freedom, c, whereas the Flory, incorporating c, gives useful predictions which form a "base-line" against which to see special effects. For instance, when component 1 is a quasi-spherical inert molecule, e.g. cyclohexane or CCl4, anomalous positive contributions occur in HE, SE and VE, but negative in CPE, ΔCv and ΔαγVT, dVE/dT and ΔγVT, while GE and dVE/dP seem little affected. These effects are usually attributed to a net decrease of structure during mixing due to a destruction of short-range orientational order in n-Cn. When component 1 is a plate-like molecule, e.g. 1,2,4-trichlorobenzene or chloronaphthalene these effects are decreased or reversed in sign. This has been ascribed to a net increase of structure due to a change of molecular conformation or a hindrance of molecular motion. When component 1 is an alcohol, the n-Cn are relatively inert while component 1 is associated in both the pure and solution states leading to + or - effects in CPE depending on whether the solution or pure component 1 is the more structured. Recently Grolier, Wilhelm and Inglese have shown that when component 1 is an ether or ketone, CPE may show an unusual concentration dependence with a double minimum, perhaps again due to molecular association or to conformational changes.

Referência(s)
Altmetric
PlumX