Study of Reactive Intermediates Using Photoacoustic Calorimetry (Chemistry)

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This grant in the Organic and Macromolecular Chemistry Program supports research by Prof. Joshua Goodman, which is aimed at the development of an experimental technique known as pulsed time-resolved photoacoustic calorimetry (PAC) and applying it to the solution of several important problems in organic chemistry and photochemistry. This work is important because the PAC technique is capable of simultaneously measuring both dynamics and energies of light-induced reactions in solution. Photochemical reactions are processes of both fundamental and practical interest, so understanding the step-by-step structural and energetic changes involved in these reactions is an important goal. Dr. Goodman's work has three principal objectives: (1) to continue development of the PAC technique by extension to non- homogeneous media and by improvement of time resolution to the 50-nanosecond regime; (2) to employ PAC techniques to measure bond dissociation energies in important chemical systems such as 1,4-biradicals, captodative radicals, and cation radicals; and (3) to determine the reactivity and energetics of non- spectroscopic reactive intermediates in cyclopropane isomerizations. These novel measurements are possible because the photoacoustic technique can time-resolve the non-radiative decay processes of reactive intermediates such as those occurring in photochemical reactions.