Res. Chem. Intermed.
, Vol. 28, No. 4, pp. 373–386 (2002)
Also available online - www.vsppub.com
Mechanism of OH radical-induced oxidation of p-cresol
to p-methylphenoxyl radical
, G. FÖLDIÁK
, M. D’ANGELANTONIO
and S. S. EMMI
Institute of Isotope and Surface Chemistry, Chemical Research Center of the Hungarian Academy
of Sciences, H-1525 Budapest, P.O. Box 77, Hungary
Istituto di Fotochimica e Radiazioni d’Alta Energia, CNR, Via P. Gobetti 101,
I-40129 Bologna, Italy
Received 23 July 2001; accepted 22 October 2001
Abstract—The OH radical-inducedoxidation of p-cresol to p-methylphenoxylradical was studied in
aqueous solution in a wide pH range by means of pulse radiolysis combined with optical spectroscopy.
OH-adduct cyclohexadienyltype radicals were identi ed as intermediatesof the reaction. In the acidic
pH range the rst-order rate coef cient of phenoxyl radical formation was found linearly dependent
on the H
concentration yielding a bimolecular rate coef cient of 1:8
the alkaline range a linear dependence was found on the OH
concentration with rate coef cient of
. These ndings were interpreted in terms of acid–base catalysis of the
O elimination from the OH-adduct. With the time resolution applied, 30 ns, the radical cation
was not observed as intermediate.
The cresol isomers are often used for studying the reactions of the reactive
intermediates of water radiolysis with phenol type compounds [1– 9]. These
reactions are essentially important in puri cation of phenol containing waste-water
by radiation treatment. The OH reactions are also often investigated from the
point of view of understanding the TiO
mediated photocatalytic decomposition
of phenolic compounds.
The OH radical-induced oxidation of phenols is a complex process that occurs
through a number of parallel and consecutive channels. The reaction possibilities
To whom correspondence should be addressed.