1973 Volume 46 Issue 9 Pages 2774-2776
The kinetics of the non-complementary reactions of Ce(IV) and Co(III) with Variamine Blue perchlorate were studied under nitrogen atmosphere in aqueous perchlorate media of ionic strength μ=2.0 M. The iminoquinone form of Variamine Blue was spectrophotometrically followed at 550 nm by stopped-flow technique. The rate constants of the stepwise reaction, Mn++(V.B.)\oversetkα\undersetkγ\ ightleftharpoonsM(n−1)++(V.B.)sox,Mn++(V.B.)sox\xrightarrowkβM(n−1)++(V.B.)ox+2H+ were evaluated at 25°C to be kα=1.7×105 and kβ=2.4×105 M−1 sec−1 for Ce4+ and kα=1.35×104 and kβ=1.53×104 M−1sec−1 at [H]=1.0 M for Co3+. The rates of Ce4+ were not affected by [H]. The [H]-dependece of kα and kβ for Co3+ gives the mechanism Coaq3++B\oversetk1\ ightleftharpoons product, CoOHaq2++B\oversetk2\ ightleftharpoons product, Coaq3+\oversetKh\ ightleftharpoonsCoOHaq2++H+, with K2\simeq107 M−1sec−1, suggesting an outer-sohere mechanism for the electron transfer with CoOH2+.
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