Photochemical generation of superoxide radicals in aqueous solutions
Superoxide (O/sub 2//sup -/) is shown to be readily generated in aqueous solutions with vacuum-uv lamps of simple design. The lamps are microwave-powered rare gas lamps emitting in the wavelength region from 165 to 185 nm. An internal Suprasil coil contains the aqueous solution. Photolysis of an oxygen-saturated formate solution yields O/sub 2//sup -/ at an initial rate of 5 to 20 ..mu..M/s depending on lamp design. The O/sub 2//sup -/ is identified by its ESR and ultraviolet absorption spectrum and also by its rate of decay in acid and base. The yield of O/sub 2//sup -/ is dependent on photolysis time, microwave power, and oxygen concentration, but is independent of formate concentration. Hydrogen peroxide is formed as a secondary product. A mechanism is proposed and shown to account for the results by comparison to computer calculations. Superoxide can also be formed in good yield by photolysis of hydrogen peroxide solutions. The photolysis of air-saturated water at pH 2 results in hydrogen sesquioxide. These lamps provide a convenient source of superoxide radicals which will facilitate studies of the reactions of this biologically important species. 6 figures, 2 tables.
- Research Organization:
- Brookhaven National Lab., Upton, NY
- OSTI ID:
- 6509255
- Journal Information:
- J. Am. Chem. Soc.; (United States), Journal Name: J. Am. Chem. Soc.; (United States) Vol. 100:18; ISSN JACSA
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
400500* -- Photochemistry
ABSORPTION SPECTRA
AQUEOUS SOLUTIONS
CARBOXYLIC ACID SALTS
CHEMICAL REACTION KINETICS
CHEMICAL REACTION YIELD
CHEMICAL REACTIONS
COMPUTER CALCULATIONS
DECOMPOSITION
DISPERSIONS
ELECTROMAGNETIC RADIATION
ELECTRON SPIN RESONANCE
ELECTRONIC EQUIPMENT
FAR ULTRAVIOLET RADIATION
FORMATES
HYDROGEN COMPOUNDS
HYDROGEN PEROXIDE
KINETICS
MAGNETIC RESONANCE
MICROWAVE EQUIPMENT
MIXTURES
OXYGEN COMPOUNDS
PEROXIDES
PH VALUE
PHOTOCHEMICAL REACTIONS
PHOTOLYSIS
QUANTITY RATIO
RADIATIONS
RADICALS
REACTION KINETICS
RESONANCE
SOLUTIONS
SPECTRA
SUPEROXIDE RADICALS
TIME DEPENDENCE
ULTRAVIOLET RADIATION
WAVELENGTHS
YIELDS