Oxidation of ascorbate anion by electron transfer to phenoxyl radicals. [2. 8-Mev electrons]

Journal Article · Tue Mar 01 04:00:00 EST 1977 · Radiat. Res.; (United States)

DOI:https://doi.org/10.2307/3574655· OSTI ID:7215632

Schuler, R H

Most phenoxyl radicals rapidly oxidize ascorbate anion (rate constants from 4 to 20 x 10/sup 8/ M/sup -1/ sec/sup -1/) by a simple electron transfer process. The product radical anion is relatively unreactive and has a well-characterized absorption at 360 nm where it has an extinction coefficient of 3300 M/sup -1/ cm/sup -1/. In the case of a phenoxyl radical produced by OH attack on phenol, oxidation appears to be quantitative. Ascorbate is oxidized only slowly or not at all by less reactive radicals, such as the alcohol radicals, para-semiquinones, or the phenyl radical. Ascorbate can, therefore, be used to selectively remove phenoxyl radicals from many mixed radical systems. Because ascorbate radical anion absorbs only weakly above 390 nm, where phenoxyl and para-semiquinone radicals absorb more strongly, ascorbate can be used to examine the oxidation of substrates in cases where phenoxyl and semiquinone radicals are produced simultaneously. This application is illustrated by a study of the attack of OH at the fluorine position of para-fluorophenol. A second illustrative example is provided by a study of the tertiary oxidation of ascorbate following reduction of the bromophenols by e/sub aq//sup -/. It is shown, in agreement with previous optical and ESR studies, that phenoxyl radicals are produced by rapid protonation of the hydroxyphenyl radical anion in the case of the ortho- and para-isomers but not in the case of the meta-isomer.

• Research Organization: Carnegie-Mellon Univ., Pittsburgh
• OSTI ID: 7215632
• Journal Information: Radiat. Res.; (United States), Journal Name: Radiat. Res.; (United States) Vol. 69:3; ISSN RAREA
• Country of Publication: United States
• Language: English

Related Subjects

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEAR CHEMISTRY
400600* -- Radiation Chemistry
ANIONS
ASCORBIC ACID
BEAMS
CHARGED PARTICLES
CHEMICAL RADIATION EFFECTS
CHEMICAL REACTIONS
CHEMISTRY
DECOMPOSITION
ELECTRON BEAMS
ELECTRON SPIN RESONANCE
ELECTRON TRANSFER
ELECTRONS
ELEMENTARY PARTICLES
ENERGY RANGE
FERMIONS
IONS
LEPTON BEAMS
LEPTONS
MAGNETIC RESONANCE
MEV RANGE
MEV RANGE 01-10
OXIDATION
PARTICLE BEAMS
PHENOXY RADICALS
RADIATION CHEMISTRY
RADIATION EFFECTS
RADICALS
RADIOLYSIS
RESONANCE
SOLVATED ELECTRONS
VITAMINS