Issue 30, 2014

Melting temperatures deduced from molar volumes: a consequence of the combination of enthalpy/entropy compensation with linear cohesive free-energy densities

Abstract

Enthalpy/entropy compensation is a general issue of intermolecular binding processes when the interaction between the partners can be roughly modelled with a single harmonic potential. Whereas linear H/S correlations are wished for by experimentalists, and often graphically justified, no inflexible law of thermodynamics supports the latter statement. On the contrary, the non-directional Ford's approach suggests logarithmic H/S relationships, which can be linearized only over narrow enthalpy/entropy ranges. Predictions covering larger domains require mathematical mapping obeying specific boundary conditions which are not compatible with linear plots. The analysis of solvent-free melting processes operating in six different classes of organic and inorganic materials shows that reciprocal Hill plots are acceptable functions for correlating melting enthalpies and entropies. The combination of H/S compensation with the observed linear dependence of the cohesive free energy densities with respect to the melting temperature eventually provides an unprecedented interdependence between melting temperatures and molar volumes. This procedure is exploited for the prediction of melting temperatures in substituted cyanobiphenyls.

Graphical abstract: Melting temperatures deduced from molar volumes: a consequence of the combination of enthalpy/entropy compensation with linear cohesive free-energy densities

Supplementary files

Article information

Article type
Paper
Submitted
13 1 2014
Accepted
18 3 2014
First published
31 3 2014
This article is Open Access
Creative Commons BY license

RSC Adv., 2014,4, 15740-15748

Melting temperatures deduced from molar volumes: a consequence of the combination of enthalpy/entropy compensation with linear cohesive free-energy densities

T. Dutronc, E. Terazzi and C. Piguet, RSC Adv., 2014, 4, 15740 DOI: 10.1039/C4RA00348A

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