Absolute rate constants for reactions of phenyl radicals

Journal Article · Wed Feb 01 04:00:00 EST 1978 · J. Am. Chem. Soc.; (United States)

DOI:https://doi.org/10.1021/ja00471a038· OSTI ID:5149063

Madhavan, V; Schuler, R H; Fessenden, R W

The absolute rate constant for the addition of p-carboxyphenyl radical to p-bromobenzoate anion in aqueous solution has been determined by optical pulse radiolysis and time-resolved ESR (electron spin resonance) experiments to be 7.6 x 10/sup 6/ M/sup -1/ s/sup -1/ (corrected to zero ionic strength). The rate constants for addition of phenyl radicals to typical aromatic systems should be of this same magnitude. Addition of p-carboxyphenyl radical to benzene occurs with a similar rate constant and results in the formation of a substituted cyclohexadienyl radical that can be quantitatively oxidized to biphenyl-4-carboxylic acid. Abstraction from hydrogen donors results in the quantitative formation of benzoic acid. By reference to the absolute rate for addition to p-bromobenzoate the rate constant for H abstraction from isopropyl alcohol has been determined from competitive measurements of benzoic acid formation to be 5.2 x 10/sup 6/ M/sup -1/ s/sup -1/. Measurements by optical pulse radiolysis and time-resolved ESR methods give comparable values. H atom abstraction from other alcohols is found to be only modestly slower. It is clear from these measurements that the lifetime of phenyl radicals in the presence of most organic materials will usually be very low so that reactions second order in phenyl radicals will not normally be important.

• Research Organization: Carnegie-Mellon Univ., Pittsburgh
• OSTI ID: 5149063
• Journal Information: J. Am. Chem. Soc.; (United States), Journal Name: J. Am. Chem. Soc.; (United States) Vol. 100:3; ISSN JACSA
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEAR CHEMISTRY
400301 -- Organic Chemistry-- Chemical & Physicochemical Properties-- (-1987)
400600* -- Radiation Chemistry
AROMATICS
ARYL RADICALS
CARBOXYLIC ACIDS
CHEMICAL RADIATION EFFECTS
CHEMICAL REACTION KINETICS
CHEMICAL REACTIONS
CHEMISTRY
DECOMPOSITION
ELECTROMAGNETIC RADIATION
ELECTRON SPIN RESONANCE
GAMMA RADIATION
IONIZING RADIATIONS
KINETICS
MAGNETIC RESONANCE
ORGANIC ACIDS
ORGANIC COMPOUNDS
PHENYL RADICALS
RADIATION CHEMISTRY
RADIATION EFFECTS
RADIATIONS
RADICALS
RADIOLYSIS
REACTION KINETICS
RESONANCE