This grant from the Organic Dynamics Program supports the research of Dr. Doubleday at Columbia University. The results of this research will provide new information about the reactions and properties of carbon-centered singlet biradical intermediates. These intermediates are produced in certain photolysis reactions and have unbonded electrons on carbon atoms that are separated by carbon chains of varying lengths. Singlet biradicals have the unbonded electrons paired, the spin array found in bonds between atoms. These intermediates have generated considerable interest recently. Comparisons will be made between experimental results and theory derived from molecular orbital calculations. Singlet biradicals will be generated by picosecond flash laser photolysis techniques from a variety of precursors, including cyclic and bicyclic azo compounds, cyclic and bicyclic hydrocarbons, cyclic sulfides, and acyclic difunctional precursors. Properties and reactions of these biradicals will be studied. The results of molecular orbital calculations will be used with canonical variational transition state theory to determine the reaction path in the decomposition of biradicals. A goal in these calculations is to explore the unusual role of entropy in the dynamics of singlet biradicals.
