Electron exchange and electron transfer of semiquinones in aqueous solutions. [pH 7]

Journal Article · Wed Nov 24 04:00:00 EST 1976 · J. Am. Chem. Soc.; (United States)

DOI:https://doi.org/10.1021/ja00440a008· OSTI ID:7232153

Meisel, D; Fessenden, R W

Rate constants for self-exchange of electrons between semiquinone radical ions and their parent quinones were measured for four benzoquinone derivatives in aqueous solutions (containing 5 M 2-propanol and 1 M acetone at pH 7). This was accomplished by measuring the effect of the concentration of the quinone on the ESR line width of the semiquinone radical ion produced by in situ photolysis. The quinones studied were benzoquinone, 2,5- and 2,6-dimethylbenzoquinone, and duroquinone. The rate constants for the electron exchange for these couples were found to be in the range of 0.5 to 2 x 10/sup 8/ M/sup -1/s/sup -1/. Electron transfer from one semiquinone to another quinone in this group of benzoquinone derivatives was measured using kinetic spectrophotometry and pulse radiolysis. Since one-electron reduction potentials for all of these quinone/semiquinone couples are known from pulse radiolysis determination of the equilibria, electron transfer rates can be predicted using the Marcus theory from rates of the self-exchange reactions. The calculated rates thus obtained are in good agreement with the experimentally measured rate constants. Reaction radii could be estimated and further correlations between the rates of electron transfer and the free energy changes were checked.

• Research Organization: Carnegie--Mellon Univ., Pittsburgh
• OSTI ID: 7232153
• Journal Information: J. Am. Chem. Soc.; (United States), Journal Name: J. Am. Chem. Soc.; (United States) Vol. 98:24; ISSN JACSA
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400301* -- Organic Chemistry-- Chemical & Physicochemical Properties-- (-1987)
AQUEOUS SOLUTIONS
AROMATICS
CHEMICAL REACTION KINETICS
CHEMICAL REACTIONS
DECOMPOSITION
DISPERSIONS
ELECTRON SPIN RESONANCE
ELECTRON TRANSFER
KINETICS
MAGNETIC RESONANCE
MIXTURES
ORGANIC COMPOUNDS
ORGANIC OXYGEN COMPOUNDS
PHOTOCHEMICAL REACTIONS
PHOTOLYSIS
PHYSICAL PROPERTIES
QUINONES
RADICALS
REACTION KINETICS
REDOX POTENTIAL
RESONANCE
SOLUTIONS
THERMODYNAMIC PROPERTIES