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KINETICS AND MECHANISMS OF THE REACTIONS OF
BENZENEDIOLS WITH BINUCLEAR OXALATOCOBALTATE (III) COMPLEX
*S Mamman
and J. F. Iyun
*Chemistry Department, University of Abuja, Abuja, Nigeria
Chemistry Department, Ahmadu Bello University, Zaria, Nigeria
ABSTRACT
The
stoichiometries for the oxidations of three benzenediols (catechol,
hydroquinone and Resorcinol) to quinone respectively, by
di-μ-hydroxobis[dioxalatocobaltate(III), (Co2(OH)2(C2O4)
44-) were determined to be 1:1 (oxidant :
reductanct) for each of the three systems, in aqueous HClO4.
Each of the reactions follows both acid-dependent and
acid-independent paths. The rates of oxidation of Catechol and
Resorcinol increase with increasing acidity while the rate of
hydroquinone oxidation is inversely dependent on [H+].
There was no evidence of either intermediate complex or free radical
formation in any of the reactions. The values of the second order
rate constants are:
k2
(Catechol) = (1.31 ± 0.03) x 10-2 dm3 mol-1s-1
k2
(Hydroquinone) = (2.47 ± 0.14) x 10-2 dm3 mol-1s-1
k2
(Resorcinol) = (3.11 ± 0.10) x 10-3 dm3 mol-1s-1
Possible
reaction steps and mechanisms are suggested.
Keywords:
mechanisms, oxidation, benezendiols, binuclear oxalatocobaltate III.
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