Although p-benzoquinone has a high electron affinity (1.9 eV), its reaction with excess electrons exhibits an unusual solvent and temperature dependence. The reaction is fast and has a positive activation energy in n-pentane but is much slower and has a negative activation energy in Si(CH/sub 3/)/sub 4/, neopentane, and 2,2,4,4-tetramethylpentane. The results can be explained in terms of an equilibrium with a short-lived excited state of the anion: e/sup -/ + benzoquinone reversible benzoquinone(-)*. The attachment rate is fast in all solvents. The reverse, autodetachment from the excited anion, is characterized by an activation energy, which depends on the value of V/sub 0/, the energy level of the electron in the liquid. For Si(CH/sub 3/)/sub 4/ for which V/sub 0/ is the lowest (-0.55 eV), the activation energy is 5.7 kcal/mol. As V/sub 0/ increases, the activation energy increases and is 9.4 kcal/mol in 2,2,4,4-tetramethylpentane for which V/sub 0/ = -0.35 eV. When V/sub 0/ is close to zero, as in n-pentane, the activation energy is so large that detachment from the excited anion state is too slow to compete with deactivation and a fast diffusion-controlled forward rate is observed. The spectrum of benzoquinone anion as observed by the lasermore » photodetachment technique is reported, and the threshold for photodetachment is found to be 2.32 eV in Si(CH/sub 3/)/sub 4/ and 2.58 eV in 2,2,4-trimethylpentane. The quantum yield of photodetachment reaches a maximum value at 480 nm in Si(CH/sub 3/)/sub 4/. 6 figures, 2 tables.« less