REACTIONS OF 12-TUNGSTOC0BALTATE(III) ANION WITH SOME ORGANIC AND INORGANIC LIGANDG IN AQUEOUS SOLUTION
REACTIONS OF 12-TUNGSTOC0BALTATE(III) ANION WITH SOME ORGANIC AND INORGANIC LIGANDG IN AQUEOUS SOLUTION
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Date
1981-04
Authors
AYOKO, GODWIN ADEFIKAYO
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Abstract
The kinetics of the reduction of 12-tungstooobaltate(iii)
anion by some organic and inorganic substrates have been
investigated in perchlorate acid media. These reactions are
shown to proceed by series of univalent changes involving
free radical intermediates. Both spectrophotometer and
kinetic observations indicate that inner-sphere complex
formation is absent and the inertness of the oxidant to
substitution is advanced as the major reason for the operation
of the outer sphere mechanism in these reactions.
in the oxidation's of butane 1,4-diiol and pennant 1,5-
idol by 12-tungstocobaltate (III) anion, only one of the
two hydroxide groups in the idols is oxidized. In contrast
to the reaction of butane 1,4-diol where no hydrogen ion
dependence is observed, the rate of oxidation nf pontnna 1,
5-diol is catalyses by acid and retarded by added 12-tungs tocobaltate
(II) ions. Rates of oxidation of pennant 1,5-diol
also correlated well with Hammett»s and Bunncttis relations
in the acid concentration range used. Mechanistic interpretation
of these observations is advanced.
One mole each of L-cysteine, Meritocratic acid and
Methamphetamine is required to reduce 12-tungstocobal Tate
(III) to 12-tungstocobaltate(II) with the disulphide of the
ligand as the other product. The rates of the reactions
decrease with increasing (H+) .This is attributed to the
dissociation of the hydrogen of the -SH group in the thistles
prior to electron transfer. possible mechanic for the
reactions and the significance of the second-order Lindy
dependent pathways observed in these reaction are discussed.
Finally, the reactions of 12-tungstocobal tats (III)
with nitrous acid, thiocyanate and iodide ions Ara first
order in both the oxidant and the reluctant in each case.
Although simple electron transfer from SCN- or _I to 12-
laughingstock (III) to give SCN or I radicals in not
thermodynamically feasible, it is kinetically favored.
possible driving forces for the reactions are suggested.
Excellent agreement is obtained between observed rate constants
and those calculated on the basis of Marcus theory far the
reactions of l- and SCN- with the oxidant,, The i- reduction
of 12-tungstocobaltate (III) is catalyzed by bromide and
chloride ions and this is rationalized in terms of possible
stabilization of atomic iodine by these ho-lido ions.
Description
A Thesis submitted to the Department of Chemistry,
Ahmadu Bello university, Zaria for the degree of
Master of Science.
APRIL, 1981
Keywords
REACTIONS,, 12-TUNGSTOC0BALTATE,, ANION,, ORGANIC,, INORGANIC,, LIGANDG,, AQUEOUS,, SOLUTION