Vapor Pressure Studies of Hydrophobic Interactions (Chemistry)

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Although hydrophobic interactions are ubiquitous and fundamentally important in a variety of chemical and biological systems, vapor pressure results are unique in that they provide unambiguous thermodynamic information about the association of hydrocarbon moieties in dilute aqueous solution. Dr. Christian will undertake extensive new solution studies, with the goal of obtaining highly-precise data for systems in which hydrophobic interactions are the predominant associative effects. By making a major improvement in the automated vapor pressure apparatus, it is planned to expand considerably the range of systems that can be investigated. Aqueous systems to be studied will include: binary solutions of individual hydrocarbons and fluorinated hydrocarbon molecules, ternary solutions containing volatile hydrocarbons and nonvolatile polar solutes (including surfactants), and very dilute solutions of aliphatic alcohols in water. This latter type of study has already yielded extremely precise vapor pressure results for methanol, ethanol, 2-propanol, and tert-butanol. Interaction parameters (Gibbs free energies, enthalpies, and entropies) for pairwise and higher-order interactions of alcohol molecules have been obtained with an accuracy that has never been attained previously. The new automated system will make it possible to obtain excellent total and partial vapor pressure results for solutions of many compounds, including the aliphatic alcohols, that are less volatile than water.