Interpretation of the thermodynamic, spectroscopic and dielectric properties of solutions of ethanol in cyclohexane in terms of association

Abstract

A model is proposed to explain the thermodynamic, spectroscopic and dielectric properties of dilute solutions of ethanol in cyclohexane in terms of association into both open-chain and cyclic hydrogen bonded groups, with allowance for a Van der Waals interaction term. It proves necessary to specify: two standard enthalpies for formation of the H-bonds, h₂=–21.2 kJ mol^–1 for the dimer and h=–23.5 kJ mol^–1 for all larger groups; three standard entropies of stepwise formation (for the dimer, trimer and all higher open-chain forms); and a standard entropy of formation from open-chain to cyclic groups, which are assumed to be present to a significant extent only for groups of more than four molecules. This model gives a quantitative reproduction of the activity coefficients, enthalpies of mixing and i.r. spectroscopic behaviour, and accounts for the initial decrease in the apparent dipole moment.