This grant from the Organic Dynamics Program supports the continuing work of Professor Martin E. Newcomb at Wayne State University. A number of very fast organic radical reactions will be studied including second order radical trapping reactions that approach the rate of diffusion in low viscosity solvents and first order rearrangements of highly reactive radicals that have lifetimes at room temperature as short as several picoseconds. An indirect kinetic method for determining rate constants of carbon- centered radical rearrangements which has been reported will be further developed such that it will have an ultimate kinetic resolution at room temperature of about one picosecond and will be useful even when direct kinetic studies are not possible. The indirect method will be extended to decarboxylations of acyloxy radicals and reactions of nitrogen-centered radicals. Fast rearrangements of aryl-substituted cyclopropyl-carbinyl radicals, substituted 5-hexenyl radicals and the cubylcarbinyl radical will be fully characterized. Applications of radical rearrangements in mechanistic studies of iron-containing enzymes and their models will be initiated. A direct laser-flash kinetic method will also be utilized to study decarboxylations of acyloxy radicals as well as rearrangements of carbon- and nitrogen-centered radicals. %%% Organic radicals, neutral species with an odd number of electrons, will be studied. These reactive species will be generated by thermolysis of stable precursor molecules. An indirect method of determining the rates of reactions of the radicals will be developed. This new rate measurement method will allow examinations of reactions of carbon and nitrogen containing radicals which were previously too rapid to study conveniently. Application of this new technology to examine iron-containing enzymes and their models will be initiated. The results are expected to provide valuable information that can be used in a wide variety of organic and biological reactions that involve radical intermediates.
