Heterogeneous association in methanol-carbon tetrachloride mixtures

A lattice model developed for the calculation of the equilibrium distribution of molecular clusters in methanol-carbon tetrachloride mixtures is modified in order to account for an entropy component associated to the binding of CCl_4 with the nondonating end of methanol clusters. This entropy contribution is shown to affect significantly the H-bonding energy estimates based on the use of the model for the analysis of both the static dielectric response and the Raman O-H stretching spectra of these mixtures. The agreement with some results from numerical simulations turns out to be improved. In particular, the new value of ~6.2 kcal/mol found for the H-bonding energy (to be compared with ~3.2 kcal/mol yielded by the previous version of the model) is close to the results of simulation (~5.5 kcal/mol). The H-bonding energy is also estimated by fitting the excess mixing enthalpy with an empirical polynomial expansion, complemented by an association contribution derived from the model. The agreement is good in this case too.