Kinetics and mechanism of the formation of manganese(III) from manganese(II) and (VII) in aqueous perchlorate solution

The reaction 4MnIIfMnVxI = 5MnIII obeyed the rate equation, rate = k[Mnu]2[MnvII]. In lithium perchlorate media the [H+]-dependence was found to be k = k~H+]+ko. Activation energies and entropies were compared with standard values for formation of intermediate species in an examination of possible mechanisms

Kinetics of the aqueous manganese(III)+ iron(II) reaction by platinum-electrode polarography

The rate equation –d[FeII]/dt=kobs[FeII][MnIII] was established by measurements of the iron(II) diffusion current. For 0.3–15°C in 0.54-3 M HClO4 the variation of kobs was consistent with the relation kobs=(ko[H+]+k1Kh)/([H+]+Kh), where Kh is the manganese(III) hydrolysis constant. Values of k0 are just less than k1 as in the comparable oxidation of vanadium(IV). It is concluded from further comparisons of rates that the activated complexes are outer-sphere

A kinetic measurement for fast cation-cation oxidations in solution

The use of rotating platinum electrodes in polarography, hitherto confined to oxidations involving only one ionic reactant can be extended to kinetic investigation of fast calomel-cation oxidations provided there exists a suitable applied voltage at which only one species gives a diffusion current..

Electron transfer reactions of vanadium(IV) with some oxyanion oxidants in aqueous perchloric acid. Part I. Reaction with chromium-(VI) and manganese(VII)

The rate law k[CrVI][VIV]2[H+]n/VV], with n < 1, is confirmed, and differences from the iron(II)–chromium(IV) result are explained. With proper interpretation the comparability of iron(II) with vanadium(IV) reactions is preserved. The reaction of vanadium(IV) with manganese(VIII) appears to be initially just of the second order, but non-stoicheiometry and acceleration by product manganese(II) introduce later complications only qualitatively resolvable

The iron(II)-chromium(VI) reaction: An additional pathway first order in iron(II)

The iron(II)–chromium(VI) reaction has been studied by platinum-electrode polarography at low (micromolar) iron(II) concentrations. Here an additional term first order in iron(II) appears in the rate equation, which is found to be –d[FeII]/dt=k1H[H+][HCrO4–][FeII]+k2H[HCrO4–][FeII]2/[Fe3+], with k1H= 234 l2 mol–4 s–1 and 10–8k2H= 6·92 l4 mol–4 s–1 at 20 °C and ionic strength 1·00 mol l–1 in sodium perchlorate medium with 0·025–0·065M perchloric acid

Manganese(III) and its hydroxo- and chloro-complexes in aqueous perchloric acid: comparison with similar transition-metal(III) complexes

At 25°C the formation constant of MnCl2+ is found by spectrophotometry to be 13.2 ± 0.9 dm3 mol–1 at ionic strength 3.26 mol dm–3; for MnCl+2 the value is 1.1 ± 0.7 dm3 mol–1. Increase in the number of chloride ions in complexes results in longer wavelengths for the corresponding absorption maxima. In the absence of chloride the hydrolysis constant of MnIII at ionic strength 5.6 mol dm–3 is found from voltammetry and potentiometry to be 1.05± 0.26 mol dm–3. Aged managanese(III) is found to be 15–25% polymeric, from both kinetic and e.m.f. measurements. Comparison of formation constants for halogeno- and hydroxo-complexes of M3+(first transition series) shows that a combination of charge-transfer, ligand-field and coulomb interactions underlies the observed sequences; the dipole moment of OH– is also a factor

Electron-transfer kinetics of the iron (II)-vanadium (V), iron (III)-vanadium (IV) system in aqueous perchlorate, by platinum-electrode polarography

Separate measurements of forward and reverse reaction rates of the reaction Fe(II)+V(V)⇄Fe(III)+V(IV)Fe(II)+V(V)⇄Fe(III)+V(IV) have been obtained at several temperatures by measurements of the Fe(II) diffusion current. These confirm that the major paths have rate terms respectively proportional to and inversely proportional to [H +], although medium effects are also apparent. An interpretation of the very low ΔH1* (1·69 Kcal/mole) for the major foward path is given in terms of a proton transfer coefficient

Anomalous activation entropy in the iron(11)-manganese(111) reaction

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