Solute ion and radical formation in the pulse radiolysis of acetonitrile solutions

Following microsecond pulse radiolysis of solutions of a variety of solutes in acetonitrile, absorptions assigned to solute cation radicals, anion radicals, excited states and neutral radicals are observed. Pulse radiolysis of solutions of tri-p-tolylamine or triphenylamine yields the amine radical cations, whose absorptions are observed to grow-in by a second-order process after the electron pulse. We report rate constants for this process, which is suggested to be electron transfer to acetonitrile radical cation or cation dimer. Yields of G∼0.2 are reported for the oxidizing species. Oxidation via a different route involving hydrogen atom transfer is suggested to occur following pulse radiolysis of solutions of phenol or phenothiazine. Pulse radiolysis of solutions of benzophenone or biphenyl yields the solute radical anions in agreement with previous studies on this system. The mechanism of acetonitrile radiolysis is discussed with a consideration of this and previous studies.