Permanganate ions

Starks reported that although no reaction was observed at room temperature between aqueous neutral KMn04 and 1-octene, when a small amount of quaternary 

Recently, the two-phase permanganate oxidation of piperonal to piperonylic acid (Eq. 11.2) has been carried out. A 65% yield was obtained when cetyltrimethylammo-nium bromide was present in the reaction mixture [5]. 

The two-phase permanganate oxidation of olefins generally affords products of oxidative cleavage. Weber and Shepherd found that when benzyltriethylammonium chloride was used as catalyst and the temperature was maintained near 0°C, internal olefins were oxidized by basic permanganate in dichloromethane to the corresponding czs-glycols in moderate yields (Eq. 11.3) [6]. Cyclohexene, c/s-cyclooctene and trans-cyclododecene were dihydroxylated by this method in 15%, 50%, and 50% yields 

Potassium permanganate can be readily solubilized in nonpolar media by complex-ing the potassium ion with a crown ether. Sam and Simmons [7] found that dicyclo-hexyl-18-crown-6 could solubilize solid potassium permanganate in benzene to the extent of about 0.06 molar. The resulting purple benzene solution was used to oxidize a number of organic substrates in good to excellent yield. Some of their results are recorded in Table 11.3. Similar results have recently been reported by other workers [8, 9]. 

18-Crown-6 catalyzes the solid-liquid permanganate oxidation of catechols in dichloromethane solution to ortho-quinones [10]. This appears to be a mild and effective method for generating these relatively unstable molecules (Eq. 11.4). 

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Uncombined elements are all given zero oxidation state. Consider (a) manganese in the permanganate ion, MnO there are four... 

Outline how you would determine the concentration of permanganate ions in the product (practical details are not required). 

An illustrative example generates a 2 x 2 calibration matrix from which we can determine the concentrations xi and X2 of dichromate and permanganate ions simultaneously by making spectrophotometric measurements yi and j2 at different wavelengths on an aqueous mixture of the unknowns. The advantage of this simple two-component analytical problem in 3-space is that one can envision the plane representing absorbance A as a linear function of two concentration variables A =f xuX2). 

The intermediate formed in the oxidation of alkenes by permanganate ion is considered a cycHc manganate(V) ester (92). Investigations have suggested that manganate(V) intermediates play a significant role in virtually all permanganate oxidation reactions. It is therefore the further reactions of the... 

The purple permanganate ion [14333-13-2], MnOu can be obtained from lower valent manganese compounds by a wide variety of reactions, eg, from manganese metal by anodic oxidation from Mn(II) solution by oxidants such as o2one, periodate, bismuthate, and persulfate (using Ag" as catalyst), lead peroxide in acid, or chlorine in base or from MnO by disproportionation, or chemical or electrochemical oxidation. 

Oxidation Reactions. Potassium permanganate is a versatile oxidizing agent characterized by a high standard electrode potential that can be used under a wide range of reaction conditions (100,133—141). The permanganate ion can participate in a reaction in any of three distinct redox couples. 

Under acidic conditions, pH < 3.5, and in the presence of certain reducing agents, the permanganate ion can undergo a five-electron exchange resulting in the divalent manganese ion. 

D. G. Lee, The Oxidation ofiOrganic Compounds by Permanganate Ion andHexavalent Chromium, Open Court Publishing Co., La SaUe, IU., 1980. 

The data on the absorption spectra of permanganate ion in different crystalline fields is interpreted in terms of the symmetries of the excited states predicted by our calculations. 

Sometimes, though, it is by no means obvious how a given half-equation is to be balanced. This commonly happens when elements other than those being oxidized or reduced take part in the reaction. Most often, these elements are oxygen (oxid. no. = — 2) and hydrogen (oxid. no. = +1). Consider, for example, the half-equation for the reduction of the permanganate ion,... 

When permanganate ions in aqueous solution react with cobalt metal in strong add, the equation for the reaction that takes place is... 

Iron(II) can be oxidized to iron(m) by permanganate ion in acidic solution. The permanganate ion is reduced to manganese(II) ion. 

In the laboratory you have observed the reaction of ferrous ion, Fe+i(aq), with permanganate ion, MnOiYaqJ, and also the reaction of oxalate ion, CiOi2(aq), with permanganate ion, MnO (aq). These studies show that the rate of a reaction depends upon the nature of the reacting substances. In Experiment 14, the reaction between IO and HSO3" shows that the rate of a reaction depends upon concentrations of reactants and on the temperature. Let us examine these factors one at a time. 

Both ferrous ion, Fe+2(aq) and oxalate ion, Cf)t2(aq), have the capability of decolorizing a solution containing permanganate ion at room temperature. Yet, there is a great contrast in the time required for the decoloration. The difference lies in specific characteristics of Ft+2(aq) and Cf 2(aq). On the other hand, Fe+2(aq) is also changed to Fe+ (aq) by reacting either with MnO fagJ or with ceric ion, Ce+i(aq). One of these reactions is simple and the other involves... 

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. 

Oxidizing agents also attack the double bond. When a reaction between an unsaturated compound and the permanganate ion occurs, the violet color of permanganate fades. This reaction, as well as reaction (29b) in which a color change also occurs, is used as a qualitative test for the presence of double bonds in compounds. 

An example of catalytic action is provided by the titration of oxalates with potassium permanganate solution referred to above. It is found that even though the oxalate solution is heated, the first few drops of permanganate solution are only slowly decolorised, but as more permanganate solution is added the decoloration becomes instantaneous. This is because the reaction between oxalate ions and permanganate ions is catalysed by the Mn2+ ions formed by the reduction of permanganate ions ... 

This enables us to calculate the effect of change in the ratio [Mn04 ]/[Mn2 + ] at any hydrogen ion concentration, other factors being maintained constant. In this system, however, difficulties are experienced in the calculation owing to the fact that the reduction products of the permanganate ion vary at different hydrogen ion concentrations. In other cases no such difficulties arise, and the calculation may be employed with confidence. Thus in the reaction ... 

The standard potential in acid solution, e, has been calculated to be 1.51 volts hence the permanganate ion in acid solution is a strong oxidising agent. 

Now the gain and loss of electrons must be equal. One permanganate ion utilises 5 electrons, and one iron(II) ion liberates 1 electron hence the two partial equations must apply in the ratio of 1 5. 

Prior equilibria. The oxidation of tris-( 1, lO-phenanthroline)iron(II) ion by permanganate ion is characterized by this rate law 18... 

Kinetic isotope effect. The oxidation of benzaldehyde by permanganate ions is believed to occur by hydride abstraction. What value of k /kD do you predict for C6H5CHO/ C6H5CDO For C6H5CHO/C6D5CHO ... 

The stoichiometric point is reached when all the Fe2+ has reacted and is detected when the purple color of the permanganate ion persists. A sample of ore of mass 0.202 g was dissolved in hydrochloric acid, and the resulting solution needed 16.7 mL of 0.0108 M KMn04(aq) to reach the stoichiometric point, (a) What mass of iron(ll) ions is present (b) What is the mass percentage of iron in the ore sample ... 

SOLUTION (a) Find the mass of iron present in the sample. From the chemical equa- tion, the stoichiometric relation between the iron and the permanganate ions is... 

Permanganate ions, Mn04, react with oxalic acid, H2C204, in acidic aqueous solution, producing manganese(II) ions and carbon dioxide. The skeletal equation is... 

The products of the reaction between bromide ions and permanganate ions, Mn04, in basic aqueous solution are solid manganese(IV) oxide, MnO>, and bromate ions. Balance the net ionic equation for the reaction. 

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