Anion radicals of aromatic ketones in amine solutions as studied by radiolysis

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Amine solutions of benzophenone and acetophenone have been studied by using matrix isolation and pulse radiolysis techniques at various temperatures. In the case of benzophenone, the anion radical produced in sec-butylamine solution at 77/sup 0/K has an absorption peak at 780 nm, whereas the peak locates at 680 nm at 153 K. The former peak is ascribed to a presolvated benzophenone anion radical and the latter to a solvated one. This solvated benzophenone anion radical was found to be in equilibrium with the ketyl radical in primary and secondary amine solutions. The enthalpy change (..delta..H) was obtained for these systems to be ca. 6 kcal/mol. In a triethylamine solution at 183 K, the benzophenone anion radical has an absorption peak at 760 nm. The equilibrium between the anion and ketyl radicals was not observed in this solution. The acetophenone anion radical in the sec-butylamine solution showed the spectral shift due to solvation. An equilibrium between the anion and ketyl radicals was also studied.