Spectroscopy and Thermochemistry of Biradicals

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An investigation of the heats of formation of a variety of biradicals will be conducted in the gas phase. The study will involve the use of laser photoionization mass spectroscopy and photoelectron spectroscopy to test the valence bond theory for biradical formation by making estimates of the singlet-triplet gap. The proposed investigation is based upon the assumption that the singlet-triplet energy gap can be obtained directly from the ionization potentials of the biradical and the parent radical intermediates. Species to be studied include benzynes, dehydrotoluenes, cycloalkynes, and a variety of other strained molecules. The reactive species will be generated in the gas phase by supersonic jet flash pyrolysis of appropriate precursors, and studied by vacuum-uv laser photoelectron and mass spectroscopy. %%% This grant from the Organic Dynamics Program supports the work of Professor Peter Chen at Harvard University. The investigation to be conducted will involve measurements of the chemical reactivity of molecules in the gas phase, and will provide information which will allow scientists to predict the direction of several important classes of chemical reactions. The chemical species to be investigated will be prepared by a technique called super-sonic jet flash pyrolysis, which results in the generation of reactive species by exposure of appropriate precursors to very high temperatures in a short time frame. The species produced are subsequently characterized by laser photoelectron spectroscopy and mass analysis. This work has profound implications for investigation of the reactivity of species which are produced in the atmosphere, and thus contributes to our understanding of processes which effect and alter the environment.