Permanganate, potassium

In Table 3.1, it was noted that permanganate (MnOq ) is a powerful oxidizing agent in basic, acidic and neutral media. In acidic solution, the reduction potential is 1.679 V or 1.491 V, but it is 0.588 V in basic solution, according to the following reactions. 

In this section, permanganate [principally potassium permanganate (KMnOq)] will be used to oxidize alkenes to 1,2-diols. It is apparent from preceding discussions that alkenes can donate an electron pair to an electrophilic center. The structure of permanganate (MnOq , 239) is best viewed as the 1,3-dipolar molecule (b O and an negative O). Reaction occurs between an alkene, which donates electrons to the electrophilic oxygen of the dipole. As the Jt-bond breaks, positive character develops on one carbon, which is attacked by 

Swem showed that the permanganate oxidation of oleic acid (245) was pH dependent. Earlier, Lapworth and Mottram oxidized oleic acid to 9,10-dihydroxy stearic acid, 246,344 jp essentially quantitative yield by what might be considered standard conditions for hydroxylation 0.1% oleic acid, no more than 1% KMnOq, short reaction time (5 min), slight excess of alkali and a reaction temperature of 0-10°C.344 Swern found that 

345 If the pU of the reaction medium was controlled to pH 9-9.5 (by addition of sulfuric acid to the hydroxide solution), a 45% yield of a mixture of 247 and 248 was produced along with 20% of 246. 

The ability to generate the cis- diol stereoselectively is important in synthesis, where the ability to position functional groups with complete control is essential. One example is the oxidation of 1,2,3,4,4a,10a (trans-4a,10a)-hexahydrophenanthrene (249) to octahydrophenanthrenediol (250) in 66% isolated yield.346 The selectivity observed in this reaction clearly indicates the bottom face of 249 to be hindered. The source of the steric hindrance is the interaction of the axial hydrogens in the adjacent ring with the incoming reagent. 

The electrochemical oxidation is carried out with an electrolyte containing potassium hydroxide (1.4 mol dm ) and potassium manganate (100-250 g dm at 60 C at an anode made from nickel or monel (Ni-Cu). The cathode is iron or steel. The anode reaction requires an unusually low current density between 5 and 15 mA cm Even so, some oxygen evolution occun and the current yields are only between 60 and 90% the material yield generally exceeds 90%  

11 A batch cell for the production of potassium pernuinganatc (Ncue Bitterfelder cell), (a) Side view, (b) View from above. 

The electrolyte is pumped through the cell with a high Reynolds number since turbulence minimizes the crystallization of the product in the cells. The electrolyte feed contains potassium hydroxide (120-150 g dm potassium manganate (50-60 gdm ) and potassium permanganate (30-35 g dm ) and in the effluent from the cell the permanganate concentration has almost doubted. 

The current efficiency is about 90%, so the effluent also contains oxygen and hydrogen (from the cathode) and to assist the escape ofgas the cell unit may be at a slight angle. 

In this celt the current density is 8.5-10 m A cm at the anode and the cathode 

The Cr(VI) oxidation of alcohols is acid catalyzed, but both under acidic or basic conditions permanganate effects the same transformation. 

KMn04 and 18-crown-6 (purple benzene) (7.10) are used to oxidize l°-alcohols and aldehydes to carboxylic acids. 

Barium permanganate (BaMn04) is also used for the oxidation of 1°- and 2°-alcohols to aldehydes and ketones, and no overoxidation is observed. 

Manganese dioxide is extensively used as an oxidizing agent for the oxidation of allylic alcohols to the corresponding aldehydes. Benzylic and unactivated alcohols are also oxidized by Mn02- 

As seen in the last example, the configuration of the double bond is conserved in the reaction. When Mn02 is used in combination with the Bestmann-Ohira reagent, activated alcohols are converted into terminal alkynes.  

There are several processes for the manufacture of potassium permanganate. Ferromanganese or manga-nese IV) oxide minerals can be used as a starting material. 

In the process utiU/.ing lerromanganese as a starting material, the manganese metal is elect rochemicahy oxidized to permanganate  

Cast ferromanganese anodes and cooled copper tube cathodes are used with an anodic current density of 23 A/dm- at a bath temperature of 2() C. The proeess is very energy intensive and is currently only operated in small units in the former States of the USSR. 

Processes utilizing manganese(lV) oxide minerals have to pass through the following stages  

The first two stages are aeeomplishcd with atmospheric oxidation, the third eleetroehcmieally. 

Although manganese dioxide is a powerful oxidizing agent, it is nevertheless capable of being itself oxidized when it is fused with a basic flux. The trioxide of manganese is acidic in nature and combines with the base to form a salt. Thus it is evident that the presence of a base favors the oxidation. 

The dioxide of manganese is neither strongly basic nor acidic in nature and shows no marked tendency to form salts. The monoxide is distinctly basic and the trioxide is distinctly acidic, so that the former forms salts with acids and the latter with bases. It follows, therefore, that in the presence of acids the dioxide has a tendency to produce salts of manganous oxide whereby an atom of oxygen is set free, and that in the presence of bases manganese dioxide has a tendency to take on another atom of oxygen in order to produce a salt of the trioxide. 

when manganese dioxide is fused with potassium hydroxide and an oxidizing agent, the salt potassium manganate is formed. This salt is soluble in water and is fairly stable as long as a considerable excess of potassium hydroxide is present but in presence of an acid — even as weak a one as carbonic acid — the 

Apparatus 4-inch sheet-iron crucible, tongs. 

2-liter common bottle, iron ring and ring stand. 

Reference to the decomposition of KMn04 has already been made in the discussion of chain branching reactions (Chap. 3, Sect. 3.2) in which the participation of a highly reactive intermediate was postulated. This work provided a theoretical explanation of the Prout—Tompkins rate equation [eqn. (9)]. Isothermal decomposition in vacuum of freshly prepared crystals at 473—498 K gives symmetrical sigmoid a time curves which are described by the expression 

Hill et al. [117] extended the lower end of the temperature range studied (383—503 K) to investigate, in detail, the kinetic characteristics of the acceleratory period, which did not accurately obey eqn. (9). Behaviour varied with sample preparation. For recrystallized material, most of the acceleratory period showed an exponential increase of reaction rate with time (E = 155 kJ mole-1). Values of E for reaction at an interface and for nucleation within the crystal were 130 and 210 kJ mole-1, respectively. It was concluded that potential nuclei are not randomly distributed but are separated by a characteristic minimum distance, related to the Burgers vector of the dislocations present. Below 423 K, nucleation within crystals is very slow compared with decomposition at surfaces. Rate measurements are discussed with reference to absolute reaction rate theory. 

Marked differences in the decomposition kinetics of fresh and aged KMn04 are attributed [464] to slight decomposition at surfaces and grain 

Using a steady-state argument, Boldyrev derived the rate expression fe,fe2[Mn04-] 

The decomposition of KMn04 is sensitive to pre-irradiation [899] by UV [396], X-rays, 7-rays, protons and neutrons. The effects of such pretreatment, which increase with dosage, are to reduce the induction period 

In the temperature range 300-500°C, a small gradual mass-loss (1-2%) was observed for all compounds in air, 02, or N2 atmospheres. The effect of changing the atmosphere altered the decomposition temperatures only slightly. It was found that when heating to higher temperatures, 600°C, the mass-loss was dependent on the atmosphere. In all cases, the total mass-loss was found to be between 5 and 6%. The stoichiometry of this reaction was assumed to be 

TheTG-DTA curves of KMn04 and KMn04/Sb mixtures have also been reported by Beck and Brown (67). 

The anode is a platinized titanium or platinum-covered base metal and the cathode is steel or another cheap metal a separator is not necessary as the reduction of perchlorate is strongly kinetically hindered and the cathode reaction is hydrogen evolution. Reported energy consumptions lie in the range 2400-3500 kWh ton The energy efficiencies are as low as 20-40%, suggesting that cell designs could well be improved. 

Potassium permanganate is widely used as an oxidizing agent, especially for oxidation in the fine-organic-chemicals industry. World production is about 40000 ton year by far the largest plant being 15000 ton year sited in the USA. The electrochemical step is the oxidation of manganate  

In this cell the current density is 8.5-10 mA cm at the anode and the cathode current density is 1.3-1.5 A cm with an undivided cell voltage of from —2.3 to 

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Isobutyl alcohol, isobutanol, 2-methyl-propanol, isopropyl carbinol, Me2CHCH20H. B.p. 108°C. Occurs in fusel-oil. Oxidized by potassium permanganate to 2-methyl-propanoic acid dehydrated by strong sulphuric acid to 2-methylpropene. 

Condy s fluid A disinfectant solution of calcium and potassium permanganates. 

Colourless prisms m.p. 130 C. Manufactured by treating maleic anhydride with water. It is converted to the anhydride by heating at By prolonged heating at 150 "C or by heating with water under pressure at 200 C, it is converted to the isomeric (trans) fumaric acid. Reduced by hydrogen to succinic acid. Oxidized by alkaline solutions of potassium permanganate to mesotartaric acid. When heated with solutions of sodium hydroxide at 100 C, sodium( )-malate is formed. Used in the preparation of ( )-malic acid and in some polymer formulations. 

In what way does a solution of hydrogen peroxide react with (a) chlorine water, (b) potassium permanganate solution, (c) potassium dichromate solution, (d) hydrogen sulphide 50 cm of an aqueous solution of hydrogen peroxide were treated with an excess of potassium iodide and dilute sulphuric acid the liberated iodine was titrated with 0.1 M sodium thiosulphate solution and 20.0 cm were required. Calculate the concentration of the hydrogen peroxide solution in g 1" ... 

When titanium dissolves in dilute hydrochloric acid, a violet solution containing titanium(III) ions is formed. This solution rapidly decolorises acidified aqueous potassium permanganate at room temperature. Titanium(IV) chloride is a colourless covalent liquid completely hydrolysed by water. Titanium(III) chloride forms hydrated titanium(III) ions in water and disproportionates when heated in a vacuum. 

Peroxides can usually be completely removed from a sample of ether by thorough shaking with aqueous potassium permanganate solution. 

If a solution of potassium permanganate containing dilute sulphuric acid is used, the purple colour disappears and the solution ultimately becomes... 

Note that many readily oxidisable compounds (e.g., aldehydes) will also decolorise alkaline potassium permanganate in the cold. 

Required Anhydrous sodium carbonate, 5 g. potassium permanganate, 10 g. benzyl chloride, 5 ml. sodium sulphite, ca. 20 g. 

Does not give Unsaturation Test with alkaline potassium permanganate (distinction from cinnamic acid, see below). 

Reduction of potassium permanganate. To a solution of uric acid in aqueous NajCO add KMnO solution drop by drop a brown precipitate of MnOj is produced immediately in the cold. 

Traces of aldehyde are produced. If ether of a high degree of purity is required, it should l>e further shaken with 0-5 per cent, potassium permanganate solution (to convert the aldehyde into acid), then with i> per cent, sodium hydroxide solution, and finally with water. 

The acetone is refluxed with successive small quantities of potassium permanganate until the violet colour persists. It is then dried with anhydrous potassium carbonate or anhydrous calcium sulphate, filtered from the desiccant, and fractionated precautions are taken to exclude moisture. 

The analytical reagent grade is suitable for most purposes. The commercial substance may be purifled by shaking for 3 hours with three portions of potassium permanganate solution (5 g. per litre), twice for 6 hours with mercury, and Anally with a solution of mercuric sulphate (2-5 g. per litre). It is then dried over anhydrous calcium chloride, and fractionated from a water bath at 55-65°. The pure compound boils at 46-5°/760 mm. 

Chakactkrisation of Unsaturatkd Aliphatic Hydrocarbons Unlike the saturated hydrocarbons, unsaturated aliphatic hydrocarbons are soluble in concentrated sulphuric acid and exhibit characteristic reactions with dUute potassium permanganate solution and with bromine. Nevertheless, no satisfactory derivatives have yet been developed for these hydrocarbons, and their characterisation must therefore be based upon a determination of their physical properties (boiling point, density and refractive index). The physical properties of a number of selected unsaturated hydrocarbons are collected in Table 111,11. 

Use a mixture of 4-5 drops of 0- 5 per cent, potassium permanganate solution and 4 ml. of dilute sulphuric acid. 

By oxidation of primary alcohols with alkaline potassium permanganate solution or with a dichromate and dilute sulphuric add, for example ... 

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