Study on the binary mixtures of alkyls alfa, omega-dihalogenated (chlorine, bromine, iodine) with n-alkanes. An improvement by considering the variation of the interaction parameter with the chain length

The mixing enthalpies of alkyl dihalides (Cl,Br,I) + n-alkanes binary liquid mixtures are examined on the basis of the UNIFAC group contribution method. All the data available in the literature for excess enthalpies and excess volumes are taken into consideration in order to interpret the behavior of the mixtures. The HEs are analyzed using several versions of the UNIFAC model using the interaction parameters already published. The predictions are acceptable in all cases for the mixtures (α,ω-dichloroalkanes + n-alkanes), however, the estimations of the HE for (α,ω-dibromo or diiodoalkanes + n-alkanes) are inadequate. Therefore, a wide data base was used to recalculate new values for alkane/halide interaction in the version of the model proposed by Rupp et al., 1984 and considering different assumptions. A substantial improve in the predictions is observed when a variation of the interaction parameter values with the chain-length of the mixtures components is taken into account. In this case, the UNIFAC model predicts the HEs of a set of 82 new systems with an over all mean error lower than 4%.