Air-Water Partitioning and Aqueous Solubility of Phenols

Relative volatilities from highly dilute aqueous solutions were measured for phenol, 2-methylphenol, 3-methylphenol, 4-methylphenol, 2,3-dimethylphenol, 2,4-dimethylphenol, 2,5-dimethylphenol, 2,6-dimethylphenol, 3,4-dimethylphenol, and 3,5-dimethylphenol at three temperatures covering the temperature range 75--100 C with a vapor-liquid equilibrium circulation still. Because of the high dilution of solutions involved, the limiting relative volatility could be determined simply as a ratio of LTV absorbances of the equilibrium vapor-phase and liquid-phase samples. In addition, the aqueous solubilities of 2,3-dimethylphenol, 2,5-dimethylphenol, 2,6-dimethylphenol, 3,4-dimethylphenol, and 3,5-dimethylphenol were measured at 20 C by a conventional batch contacting technique with analysis by LTV spectroscopy. The vapor-liquid equilibrium data and solubilities measured in this work and some additional data from the literature were used to obtain limiting activity coefficients A, Henry`s law constants H, and air-water partition coefficients K{sub aw} covering a range of temperatures from the ambient to the normal boiling point of water. For each phenol, the temperature dependence of A, H, and K{sub aw} was used to estimate the limiting partial molar excess enthalpies and enthalpies of hydration. The values of A, H, and K{sub aw} for isomeric cresols and xylenols were found to be well correlated with their normal boiling temperatures.