Experimental Determination and Mechanistic Implications of the Thermochemistry of Singlet Carbenes

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This grant in Organic and Macromolecular Chemistry provides support for the research work of Dr. Peter Chen, Harvard University. This work focuses on using laser techniques to determine both the strengths of chemical bonds and stabilities of a number of important molecules. Specifically, this work will (1) develop and exploit gas-phase laser spectroscopic techniques for determination of bond strengths, heats of formation, and excited-state energies for medium-to-large polyatomic molecules and reactive intermediates, (2) determine the C=C homolytic bond dissociation energy of heteroatom-substituted olefins, and singlet-triplet gaps for the corresponding singlet ground-state nucleophilic carbenes, (3) test the relationship proposed by Simons and Goddard between the homolytic bond dissociation energy of an olefin to a pair of carbenes and the singlet-triplet gap in those carbenes by direct application of thermochemical data, and (4) determine key thermochemical quantities necessary to assess the importance of an electron-rich olefin/nucleophilic carbene equilibrium in reactions catalyzed by thiazolium salts.