A thermometric investigation of the association equilibria of alcohols in hydrocarbons

The molar excess enthalpy has been determined at 298.15 K for binary mixtures of butanol, pentanol, and decanol in benzene and cyclohexane, respectively, as well as for decanol in octane. Since the hydrogen association equilibrium is expected to dominate in the dilute alcohol solutions the change in apparent molar enthalpy is interpreted in terms of aggregation. It is found that the trimer is the most probable associate in all systems. The models used were, however, not able to discriminate tetramerization from the trimerization process. Furthermore, dimers may significantly contribute to the properties of the benzene systems. The equilibrium constant is strongly dependent on the system considered. For solutions rich in alcohol the apolar interaction between hydrocarbons and associated alcohol is found to be important. The effect is discussed in relation to the total contribution of structural mismatching of the components to the excess enthalpy of the system. © 1986 American Chemical Society.