Manganese dioxide permanganate

Suspend in a round-bottomed flask 1 g. of the substance in 75-80 ml. of boihng water to which about 0 -5 g. of sodium carbonate crystals have been added, and introduce slowly 4 g. of finely-powdered potassium permanganate. Heat under reflux until the purple colour of the permanganate has disappeared (1-4 hours). Allow the mixture to cool and carefully acidify with dilute sulphuric acid. Heat the mixture under reflux for a further 30 minutes and then cool. Remove any excess of manganese dioxide by the addition of a little sodium bisulphite. Filter the precipitated acid and recrystallise it from a suitable solvent (e.g., benzene, alcohol, dilute alcohol or water). If the acid does not separate from the solution, extract it with ether, benzene or carbon tetrachloride. 

Aromatic aldehydes react with the dimedone reagent (Section 111,70,2). All aromatic aldehydes (i) reduce ammoniacal silver nitrate solution and (ii) restore the colour of SchifiF s reagent many react with sodium bisulphite solution. They do not, in general, reduce Fehling s solution or Benedict s solution. Unlike aliphatic aldehydes, they usually undergo the Cannizzaro reaction (see Section IV,123) under the influence of sodium hydroxide solution. For full experimental details of the above tests, see under Ali-phalic Aldehydes, Section 111,70. They are easily oxidised by dilute alkaline permanganate solution at the ordinary temperature after removal of the manganese dioxide by sulphur dioxide or by sodium bisulphite, the acid can be obtained by acidification of the solution. 

The overall decomposition of solid potassium permanganate ia the temperature range of 250—300°C leads to the formation of a delta-manganese dioxide (shown ia brackets) and can be represented as follows ... 

Aqueous potassium permanganate solutions are not perfectiy thermodynamically stable at 25°C, because Mn02, not MnO is the thermodynamically stable form of manganese in water. Thus permanganate tends to oxidize water with the evolution of oxygen and the deposition of manganese dioxide, which acts to further catalyze the reaction. 

Total world capacity for electrolytic manganese dioxide (FMD) is estimated to be in the area of 194, 500 t/yr, and aimual capacity of chemical manganese dioxide (CMD) is estimated to be in the range of 40,000 t. Producers are fisted in Tables 18 and 19, respectively. Capacity and process information on potassium permanganate is given in Table 17. 

Oxidation. Nitroparaffins are resistant to oxidation. At ordinary temperatures, they are attacked only very slowly by strong oxidi2ing agents such as potassium permanganate, manganese dioxide, or lead peroxide. Nitronate salts, however, are oxidi2ed more easily. The salt of 2-nitropropane is converted to 2,3-dimethyl-2,3-dinitrobutane [3964-18-9], acetone, and nitrite ion by persulfates or electrolytic oxidation. With potassium permanganate, only acetone is recovered. 

The precipitated manganese dioxide and sulfur are discarded. The solution is used until it becomes spent or so low in potassium permanganate that it is no longer effective and is discarded and replaced. It is customary to place two scmbbers in series, with the Hquid flow countercurrent to the gas flow, to more efficiendy use the permanganate solution. When the solution in the first scmbber is spent, with respect to the gas, the positions of the scmbbers are... 

Oxidation. Citric acid is easily oxidized by a variety of oxidizing agents such as peroxides, hypochlorite, persulfate, permanganate, periodate, hypobromite, chromate, manganese dioxide, and nitric acid. The products of oxidation are usually acetonedicarboxyhc acid (5), oxaUc acid (6), carbon dioxide, and water, depending on the conditions used (5). 

Powdered potassium permanganate (94 mg) is added to an ice-cold, stirred solution of 0.1 g of the unsaturated nitrile in 3.5 ml of acetone containing 0.11 ml of piperidine. The reaction mixture is stirred at 0° for 1.5 hr, allowed to warm to room temperature (30 min) and then treated with 0.02 ml of acetic acid in 0.2 ml of acetone. After stirring at room temperature for an additional 1.5 hr the mixture is treated with chloroform, aqueous sodium bisulfite and sufficient 1 N sulfuric acid to reduce all of the manganese dioxide. 

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