Electron attachment to p-benzoquinone and photodetachment from benzoquinone anion in nonpolar solvents. [Pulse radiolysis followed by second pulse from tunable dye laser occurring after a delay of 10 to 200. mu. s]

Journal Article · Thu Sep 02 04:00:00 EDT 1982 · J. Phys. Chem.; (United States)

DOI:https://doi.org/10.1021/j100215a011· OSTI ID:6335932

Holroyd, R A

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 laser 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.

• Research Organization: Brookhaven National Lab., Upton, NY
• OSTI ID: 6335932
• Journal Information: J. Phys. Chem.; (United States), Journal Name: J. Phys. Chem.; (United States) Vol. 86:18; ISSN JPCHA
• Country of Publication: United States
• Language: English

Related Subjects

2-2-DIMETHYLPROPANE
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEAR CHEMISTRY
400500 -- Photochemistry
400600* -- Radiation Chemistry
ABSORPTION SPECTRA
ACTIVATION ENERGY
ALKANES
ANIONS
AROMATICS
CHARGED PARTICLES
CHEMICAL RADIATION EFFECTS
CHEMICAL REACTION KINETICS
CHEMICAL REACTION YIELD
CHEMICAL REACTIONS
CHEMISTRY
COMPARATIVE EVALUATIONS
DATA
DECOMPOSITION
ELECTRON ATTACHMENT
ELECTRON DETACHMENT
ENERGY
ENERGY-LEVEL TRANSITIONS
EXCITATION
EXPERIMENTAL DATA
HYDRIDES
HYDROCARBONS
HYDROGEN COMPOUNDS
INFORMATION
IONIZATION
IONS
IRRADIATION
KINETICS
MEDIUM TEMPERATURE
NUMERICAL DATA
ORGANIC COMPOUNDS
ORGANIC OXYGEN COMPOUNDS
ORGANIC SOLVENTS
PENTANE
PHOTOCHEMICAL REACTIONS
PHOTOIONIZATION
PHOTOLYSIS
PULSED IRRADIATION
QUINONES
RADIATION CHEMISTRY
RADIATION EFFECTS
RADIOLYSIS
REACTION KINETICS
SILANES
SILICON COMPOUNDS
SOLVENTS
SPECTRA
TEMPERATURE DEPENDENCE
YIELDS