Manganate ions

An important function of manganous ions is the ready reduction of alkylperoxy radicals (181) (eq. 34). 

Iron and Manganese Removal. Soluble ferrous and manganous ions are oxidized by ozone (typicaUy 2.5 ppm) to less soluble higher... 

Aqueous solutions can be stabilized against viscosity loss by addition of 5—10 wt % anhydrous isopropyl alcohol, ethanol, ethylene glycol, or propylene glycol. The manganous ion (Mn " ) also is an effective stabilizer at concentrations of 10 -10 wt% of the solution. 

The manganous ion [16397-91 -4] in solution then reacts with higher valent manganese oxide and zinc ions in solution to form a new phase called... 

Use oxidation numbers to balance the reaction between ferrous ion, Fe+2, and permanganate ion, MnOr, in acid solution to produce ferric ion, Fe+3, and manganous ion, Mn+2. 

However, the ability to act as a builder encompasses much more than so far been mentioned. Builders influence the coagulation of solid soil, often form a buffer system, and promote the soil suspending activity of washing liquors. They are further able to reduce the catalytic effect of ferric and manganic ions. Thus they support the stabilization of peroxides in detergents. Similarly, rancidness caused by catalytic processes of soap and fragrances can be avoided. 

Manganese Mn(II) Mn ", MnC03(s) (manganous ion, manganous carbonate solid)... 

The reaction of the permanganate and manganous ions can take place under conditions where either Mn02(s) or Mn(III), which decomposes slowly, are the main products, viz. 

In acidic solution MnOj is usually the end product, although particularly vigorous reductants, e.g. iodide and oxalate ions, convert permanganate to manganous ions. Mn(III) is stable only in acidic solution or in the form of a complex, e.g. with pyrophosphate ion, and it has seldom been reported as the end product of a permanganate oxidation, e.g. for that of Mn(II) in a phosphate buffer and for those of alcohols and ethers in the presence of fluoride ion. ... 

The apparent first-order rate coefficient obtained using excess oxidant increased exponentially with increase in acidity in the range 5 N < [H30" ] < 12 N. The reaction is first-order with respect to added manganous ions (k increasing sharply), but the activation energy (11.0 kcal.mole ) remains unchanged. At appreciable catalyst concentrations the reaction becomes almost zero-order with respect to bromide ion. The mechanism appears to be a slow oxidation of Mn(II) to Mn(III) followed by a rapid reduction of the latter by bromide. This reaction is considered further in the section on Mn(II)-catalysis of chromic acid oxidations (p. 327). 

Westheimer has also reviewed the induced oxidations by the Cr(VI)-As(III) couple of iodide, bromide and manganous ions vide supra). The induction factor of 0.5 for Mn(II) implies an intermediate tetravalent chromium species however, the factor of 2 for iodide points to a pentavalent chromium intermediate. Both... 

The oxidation induces the oxidation of manganous ion to Mn02 with an induction factor (see p. 280) of 0.5 . The rate of reduction of Cr(VI) is reduced simultaneously to a maximum extent of 50... 

The permanganate oxidation of phenols is complicated by the intervention of lower oxidation states of manganese, (c/. the oxidation of toluene, p. 298). For example, the oxidation of 2,6-dinitrophenol in weakly acidic solution displays an induction period, following second-order kinetics thereafter. However, addition of potassium fluoride inhibits reaction almost completely, but manganous ions strongly accelerate it. 

Early work of Dhar established that oxidation of oxalic acid by chromic acid occurs readily, but some of his kinetic data are unreliable as the substrate itself acted as the source of hydrogen ions. The reaction is first-order in oxidant and is subject to strong manganous ion catalysis (as opposed to the customary retardation), the catalysed reaction being zero-order in chromic acid. This observation is related to those found in the manganous-ion catalysed oxidations of several organic compounds discussed at the end of this section. 

The permanganate oxidation of oxalic acid has been studied exhaustively and has been reviewed by Ladbury and Cullis . It is characterised by an induction period and a sigmoid dependence of rate upon time. Addition of manganous ions eliminates the induction period and produces first-order decay kinetics . Addition of fluoride ions, however, practically eliminates reaction . ... 

The rate of oxidation is reduced by one half on addition of manganous ions and the following Arrhenius parameters were recorded... 

Dhar noted that the oxidation of oxalic acid by chromic acid is markedly accelerated on adding manganous ions, the reaction order in Cr(VI) changing from one to zero. Bobtelsky and Glasner ° found the oxidation of bromide ions by chromic acid in aqueous sulphuric acid to follow kinetics... 

The oxidation of oxalic acid by mercuric chloride to give CO2 and mercurous chloride is a classic example of an induced reaction. This reaction is extremely slow unless small quantities of chromic acid and manganous ions are added, whereon facile reduction takes place Addition of permanganate or persulphate and some reducing agents is also effective and the oxidation proceeds readily under photo- or X-irradiation (Eder s reaction). The large quantum yield points to a chain mechanism , which could also function with an inducing oxidant, viz. 

The kinetics of the initial stages of the oxidation of some a-hydroxy-carboxylic such as lactic, malic and mandelic acids by chromic acid have been studied by Bakore and Narain . The initial reaction resembles the oxidation of a secondary alcohol to ketone. The authors concluded that the rate determining step involves C-H bond rupture at the a-carbon atom. The rate of oxidation of these acids is reduced to one-half by the addition of manganous ions, when the concentration of the latter is commensurable with that of the acids. 

The oxidation of tartaric and glycollic acid by chromic acid also induces the oxidation of manganous ions. In the presence of higher concentrations of manganese(II) the rate of oxidation of the acids is diminished to about one-third of that in the absence of manganous ions. The decrease of the rate has been attributed to manganese(II) catalysis of the disproportionation of the intermediate valence states of chromium probably chromium(IV). 

The proposed mechanism for the functionality of MnP involves the oxidation of manganous ions Mn2+ to Mn3+, which is then chelated with organic acids. The chelated Mn3+ diffuses freely from the active site of the enzyme and can oxidize secondary substrates [25],... 

Provided that manganese is present predominantly as manganous ion, the kinetic model predicts a second-order dependence on [Mn(II)]... 

Assuming standard conditions, what is E for a cell in which iron metal reacts with manganous ion to form ferrous ion and manganese metal ... 

An acidic bromate solution can oxidize various organic compounds and the reaction is catalyzed by species like cerous and manganous ions that can generate 1-equivalent oxidants with quite positive reduction potential. Belousov (1959) first observed oscillations in Celv]/[Cem] during Ce (III) catalysed oxidation of citric acid by bromate ion. Zhabotinskii made extensive studies of both temporal and spatial oscillations and also demonstrated that instead of Ce (III), weak 1- equivalent reductants like Mn(II) and Fe (II) can also be used. The reaction is called Belousov-Zhabotinskii reaction. This reaction, most studied and best understood, can be represented as... 

The effect of valence is shown in Fig. 4. Here corresponding salts of manganous and manganic ions aie compared as acetates and as acetyl aceto-nates. The higher valence spectra appear still to be of type I, but the peaks are broadened and shifted to higher energies. The main maximum appears... 

In the field of organic ligands the oxidation of oxalic acid ligated to different central atoms provides us with almost any pattern of behavior of oxidized ligands. The oxidation of oxalate by permanganate in the presence of manganous ions (/, 68) proceeds according to Mechanism 10... 

Poly(acrylic acid) (PAA) with an average molecular weight of 250,000 was used to coat a dry tablet of ZnS Mn, which was obtained by compressing the powder at 173 MPa. The amount and state of doped manganous ion, Mn(II), was examined by electron paramagnetic resonance spectroscopy (EPR). EPR enables us to gather various extra information with respect to the state of Mn(II). 

In Fig. 18, the experimental dependence of T2 on temperature in a manganous ion solution is presented and compared with the theoretical relation. Agreement is good and these data permit an evaluation of the... 

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