Professor William Jorgensen is supported by a grant from the Theoretical and Computational Chemistry Program to perform theoretical studies of organic chemical reactions both in the gas phase and in solution using a combination of quantum mechanics, statistical mechanics and molecular dynamics simulations. The results of this theoretical research provide an important interpretation of chemical reactivity at the fundamental molecular level of understanding. Jorgensen employs ab initio molecular orbital calculations to provide energy surfaces for reactions in the gas phase and potential functions that describe solute-solvent interactions. The effect of solvation is then determined by computing the free energy surfaces in solution. This involves Monte Carlo or molecular dynamics simulations for the reacting systems plus about 300 solvent molecules in a periodic cell. Finally, the reaction dynamics are studied by trajectory calculations that are started in the transition state regions. These computations provide detailed information on key issues including the reaction mechanisms in the gas phase and in solution, the existence of intermediates, the origin of solvent induced activation barriers, changes in solvation along reaction paths, energy redistribution during reactions, and the dynamic role of the solvent in determining reaction kinetics.
