This award is made to Dr. Philip G. Jessop of the Chemistry Department, University of California, Davis, for investigation of the dependence of the selectivity of some organic reactions on the pressure of near-critical supercritical fluids (SCFs). The award is in the Technology for Sustainable Environment component of the EPA/NSF Partnership for Environmental Research, and support is provided by the MPS Organic Dynamics Chemistry Program and Office of Multidisciplinary Activities. Homogeneously catalyzed asymmetric syntheses, such as cyclopropanation, deprotonation, and alkylation reactions, will be studied. The pressure dependence of enantio- or diastereo- selectivity will be tested as the critical point of the solution is approached. For each system that shows a pressure dependence, the effect of several additional parameters will be determined, including temperature, choice of SCF (carbon dioxide, xenon or fluoroform), side groups on the ligands, choice of substrate, and use of binary supercritical fluid mixtures as reaction media. Activation volumes will be calculated from the effect of pressure on reaction rates. Many organic compounds are asymmetric, that is, can be present in right- or left-handed forms. Particularly in pharmaceutical applications, it is important to synthesize the specific form that has the desired biological effectiveness. If the correct form can be made with high selectivity, then the industrial process is more efficient, both economically and environmentally. In this project, supercritical fluids, some of which have low environmental impact, will be tested for their suitability as solvents for a variety of asymmetric organic reactions.
