I. Photochemical Studies on Phenoxy Radical. II. The Photoreaction of Michler's Ketone with Benzophenone

Citation

Wamser, Carl Christian (1970) I. Photochemical Studies on Phenoxy Radical. II. The Photoreaction of Michler's Ketone with Benzophenone. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/390h-jd89. https://resolver.caltech.edu/CaltechETD:etd-02272009-093235

Abstract

NOTE: Text or symbols not renderable in plain ASCII are indicated by [...]. Abstract is included in .pdf document. I. Photochemical studies of phenoxy radical: Phenoxy radical was generated by flash photolysis of aqueous phenol. The ultraviolet-visible absorption spectrum of phenoxy radical was obtained. Decay kinetics for the bimolecular disappearance of phenoxy radical led to a second order rate constant of k[...] = 1.2 ± 0.1 x [...] sec[...]. In these solution-phase flash photolysis studies, no evidence was obtained for further decomposition of phenoxy radical. Molecular orbital symmetry correlations demonstrate that the conversion of phenoxy radical to cyclopentadienyl radical and carbon monoxide is symmetry-allowed from the ground state and symmetry-forbidden from the excited state of phenoxy radical. II. The photorecation of Michler's ketone with benzophenone: Michler's ketone (4,4'-bis[dimethylamino]benzophenone) undergoes a photoreaction with benzophenone in 2-propanol to give photoproduct I with moderate quantum efficiency. This product arises from the coupling of benzophenone [...] ketyl radical with the corresponding radical derived from Michler's ketone. Each of these photointermediates was characterized by the absorption spectra and decay kinetics obtained from flash photolysis studies. The key mechanistic step must be transfer of hydrogen from the triplet state of Michler's ketone to benzophenone, and is without precedent in photochemistry. A triplet "exciplex" is postulated to lead to the hydrogen transfer.

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