Order destruction and order creation in binary mixtures of non-electrolytes

Abstract

Order-destruction and order-creation during mixing are discussed for binary mixtures of various liquids (component 1) with the n-alkane series (component 2). When component 1 is a spherical molecule liquid, e.g. cyclohexane, anomalous positive contributions occur in H E and S E, but negative ones occur in C P E, Δ C V, d V E/d T and other second-order quantities. The Flory theory is used as a first approximation to the prediction of these quantities. Thermodynamic effects, not included in the theory, are attributed to a net decrease in structure during mixing because of a destruction of short-range correlations of molecular orientations (CMO) in pure n-C n . When component 1 is a plate-like molecule, e.g. 1-chloronaphthalene, these effects are decreased and reversed in sign. This has been ascribed to a net increase in structure because of a hindrance to molecular motion or a change in molecular conformation. When component 1 is a linear or branched alcohol, the n-C n are relatively inert while component 1 is associated in both the pure and solution states leading to positive or negative effects in C P E depending whether the solution or pure component 1 is more structured. The Treszczanowicz-Kehiaian model for self-associated liquids + inert solvents explains these results and also provides a general framework for the discussion of both the process of order-creation and the process of order-destruction in solution.