Pg. Tratnyek et J. Hoigne, KINETICS OF REACTIONS OF CHLORINE DIOXIDE (OCLO) IN WATER .2. QUANTITATIVE STRUCTURE-ACTIVITY-RELATIONSHIPS FOR PHENOLIC-COMPOUNDS, Water research, 28(1), 1994, pp. 57-66
Chlorine dioxide (OClO) rapidly oxidizes substituted phenoxide anions
in aqueous solution and second-order rate constants for this reaction
have recently been reported for 25 compounds. Analysis of these data f
or correlations reveals several quantitative structure-activity relati
onships (QSARs) that can be used to predict rate constants for the rea
ction of additional phenolic compounds with chlorine dioxide. The rate
constants for oxidation of phenoxide anions give good Hammett correla
tions to sigma- constants and Marcus correlations using half-wave oxid
ation potentials. Ortho- as well as meta- and para-substituted phenoxi
des have been included in both types of correlations and the only outl
iers are compounds that exhibit strong intramolecular hydrogen bonding
. The results of the Marcus correlation analysis are consistent with t
he expected mechanism of reaction where the rate-limiting step is sing
le electron-transfer from the phenoxide anion to chlorine dioxide. The
second-order rate constants for oxidation of the undissociated forms
of substituted phenols are about six orders of magnitude smaller than
the corresponding values for phenoxide anions, indicating that only th
e reaction of phenoxide anions will be significant under the condition
s of water treatment with chlorine dioxide. The rate constants for und
issociated phenols also have much greater relative uncertainties than
those for the phenoxide anions, and give much less satisfactory correl
ations.