Susan Tucker is supported by an NSF Young Investigator Grant from the Theoretical and Computational Chemistry Program to study solvent effects on solute reactivity in supercritical fluids. In the supercritical regime, solvent properties vary dramatically, but continuously, with modest changes in temperature and pressure. Tucker will use computer simulation techniques, such as reactive flux molecular dynamics and umbrella sampling Monte Carlo, to explore the microscopic details of both dynamic and static solvent effects on solute reaction rates. Initially she will focus on the hydrolysis of alkyl aryl ethers, e.g. anisole, 2-methoxynaphthalene, in supercritical water. The rates of these charge transfer reactions are sensitive to solvent properties, and thus provide a stringent test of theoretical predictions. These reactions have also been subjected to extensive experimental studies. In addition, mathematical models for solvent effects within the generalized Langevin equation and the Caldeira-Leggett/Zwanzig Hamiltonian will be explored in order to develop new theories for describing the effect of changing solvent properties on solute reactivity. Supercritical fluids have found widespread application in many industrial extraction processes. They are also being used for environmental remediation. A unified theoretical description of the unique behaviors observed in supercritical fluid solvents would provide a significant contribution to predicting how thermodynamic conditions might affect solute reactivity in supercritical fluids, and aid in the development of industrial processes which make use of these technologically important solvents.
