This project is in the Inorganic, Bioinorganic and Organometallic Chemistry Program. The project is concerned with the development of a new technique called pulsed-accelerated- flow spectroscopy for the measurement of the rates of very fast irreversible chemical reactions in solutions. A key feature of the method is the variation of flow velocity to resolve mixing processes from chemical rate processes. The present capability of the technique allows the study of reactions with half-lives as short as 4 microseconds, or about 1000-fold faster than can be studied by stopped-flow techniques. The new technique allows the study of a large number of important reactions which were previously too fast to measure. The design of the pulsed-accelerated-flow spectrometer will be modified in an effort to reduce the volume of solution required for a rate measurement and to allow the measurement of half-lives even shorter than 1 microsecond. The effects of flow velocity on mixing and on light scattering due to differences in refractive index of reactants and solvents will be determined. A major effort will be the study of rapid non-metal reactions, with emphasis on the mechanisms of halogen cation (X+) transfer from nitrogen, oxygen and other halogens to a variety of nucleophiles. Acid or base catalysis of these reactions will be investigated. The effect of initial halogen bond strength, the basicity of the oxidant, and the nucleophilicity of the reductant on relative rates will be determined. The mechanisms of breakpoint clorination will be investigated. Additional studies of Ni(III) complexes, of the kinetic advantage of inner-sphere bridging, and of other fast electron-transfer and metal ion substitution reactions will be pursued also.
