Ultralow temperature effect on proton transfer reaction to benzene anions in gamma-irradiated ethanol glass

Abstract A proton transfer reaction to benzene anions in γ-irradiated ethanol was studied at 4.2 K by ESR. When an ethanol-benzene (5 mol.%) mixture is γ-irradiated at 4.2 K, benzene anions formed could be detected by ESR. Then, when the irradiated mixture is annealed at 77 K, the benzene anions change into cyclohexadienyl radicals. This observation indicates clearly the occurrence of the proton transfer reaction C 6 H - 6 +C 2 H 5 OH→C 6 H 7 +C 2 H 5 O - at 77 K. When the benzene anions are illuminated with tungsten light at 4.2 K, the anions change into cyclohexadienyl radicals even at 4.2 K. The results were interpreted in terms of a proton transfer reaction to excited benzene anions (C 6 H -∗ ), formed by the illumination of light; C 6 H -∗ 6 +C 2 H 5 OH→C 6 H 7 +C 2 H 5 O - . The rate for the proton transfer reaction C 6 H - 6 +C 2 H 5 OH→C 6 H 7 +C 2 H 5 O - was studied by electron-pulse radiolysis at low temperatures. The proton transfer reaction to benzene anions takes place in a time shorter than 300 ns at 80 K, though the reaction is suppressed at 4.2 K.