Manganese dioxide, preparation

Mixtures with mercury (II) oxide and manganese dioxide prepared at — 80°C ignited at 20° and reacted violently at 15°C, respectively. Copper(II) oxide reacted vigorously at 25 °C without ignition. 

Similar behavior has been observed with different modifications of Mn(IV) oxides. The cryptomelane type of hydrous manganese dioxide prepared by the reaction of Mn(II) and KMn04 in sulfuric acid solution exhibits an extremely high selectivity for potassium ions [120]. The spinel type of manganese oxide prepared by the introduction of lithium ion has exhibited an extremely high selectivity for lithium ion [121, 122]. These aspects are considered later. 

Oxidation of allylic or benzylic alcohols. Manganese dioxide prepared by ozoniza-tion of manganese (II) nitrate is an effective agent for oxidation of allylic and benzylic alcohols.38... 

Oxidation of nitrogen compounds [bottom of 1, 640], Bhatnagar and George2011 found that chalcone phenylhydrazones are oxidized to pyrazoles in good yield by active manganese dioxide prepared according to Pratt and McGovern.19 Benzala-... 

In the laboratory it can be prepared by the electrolysis of water or by heating potassium chlorate with manganese dioxide as a catalyst. 

Acetaldehyde [75-07-0] (ethanal), CH CHO, was first prepared by Scheele ia 1774, by the action of manganese dioxide [1313-13-9] and sulfuric acid [7664-93-9] on ethanol [64-17-5]. The stmcture of acetaldehyde was estabhshed in 1835 by Liebig from a pure sample prepared by oxidising ethyl alcohol with chromic acid. Liebig named the compound "aldehyde" from the Latin words translated as al(cohol) dehyd(rogenated). The formation of acetaldehyde by the addition of water [7732-18-5] to acetylene [74-86-2] was observed by Kutscherow] in 1881. 

Electrolytic Manganese Dioxide. The anodic oxidation of an Mn(II) salt to manganese dioxide dates back to 1830, but the usefuhiess of electrolyticaHy prepared manganese dioxide for battery purposes was not recognized until 1918 (69). Initial use of electrolytic manganese dioxide (EAfD) for battery use was ia Japan (70) where usage continues. 

The preparation of triaryknethane dyes proceeds through several stages formation of the colorless leuco base in acid media, conversion to the colorless carbinol base by using an oxidising agent, eg, lead dioxide, manganese dioxide, or alkah dichromates, and formation of the dye by treatment with acid (Fig. 1). The oxidation of the leuco base can also be accompHshed with atmospheric oxygen in the presence of catalysts. 

Syntheses in Solvent Systems. Very few examples of syntheses of metal carbonyls in aqueous solution are reported. An exception is the preparation of Co2(CO)g from CoSO (66% yield) or C0CI2 (56% yield) and CO at 9.6—11 MPa (95—110 atm) in aqueous ammonia at 120°C for 16—18 h (101). Triiron dodecacarbonyl is prepared almost exclusively in aqueous solution. Quantitative yields of Fe2(CO)22 have been obtained by oxidising alkaline solutions of carbonyl ferrates with manganese dioxide (102—104). 

Purpurin [81-54-9] (179) is a usefiil iatemiediate for preparing acid-mordant dyes, and is prepared by oxidation of alizarin with manganese dioxide and sulfuric acid (145). 

Isoxazole-5-carbaldehyde was prepared by the manganese dioxide oxidation of 5-hydroxymethylisoxazole (67T4697), the latter being formed from sodium fulminate and propargyl alcohol in greater than 90% yield. 

Thymoquinone has been prepared directly from thymol by sulfonating and oxidizing the sulfonation mixture with manganese dioxide or potassium dichromate the same process has been successfully applied to carvacrol. The oxidation of sa ts of aminothymol with dichromate, ferric chloride, or nascent bromine also leads to satisfactory yields of thymoquinone. The above procedure is based on the observation that the diazonium salt obtained from aminothymol is almost quantitatively con-... 

The procedure described is that of Wille and Saffer. Propiolaldehyde has also been prepared by the oxidation of propargyl alcohol using ammonium dichromate or manganese dioxide in 10% sulfuric acid. Propiolaldehyde has also been prepared by warming the dimethyl or diethyl acetal with dilute sulfuric acid. ... 

Oxygen occurs free in air in which it forms 21% by volume. It is also found combined with hydrogen in water and constitutes 86% of the oceans, and with other elements such as minerals constituting ca 50% of the earth s crust. In the laboratory it is usually prepared by the thermal decomposition of potassium chlorate in the presence of manganese dioxide catalyst ... 

Nickel peroxide is a solid, insoluble oxidant prepared by reaction of nickel (II) salts with hypochlorite or ozone in aqueous alkaline solution. This reagent when used in nonpolar medium is similar to, but more reactive than, activated manganese dioxide in selectively oxidizing allylic or acetylenic alcohols. It also reacts rapidly with amines, phenols, hydrazones and sulfides so that selective oxidation of allylic alcohols in the presence of these functionalities may not be possible. In basic media the oxidizing power of nickel peroxide is increased and saturated primary alcohols can be oxidized directly to carboxylic acids. In the presence of ammonia at —20°, primary allylic alcohols give amides while at elevated temperatures nitriles are formed. At elevated temperatures efficient cleavage of a-glycols, a-ketols... 

Kubota and co-workers also prepared several 1,2-diols (61) and noted that these substances give the enediones (59) in much better yields than the diosphenols (58). This is consistent with a mechanism which requires, as the first step, hydroxylation of the -double bond of (58) by manganese dioxide followed by oxidation to the intermediate trione. 

Commercially available hydrogen fluoride usually is not suitable for catalytic hydrogenation because of its sulfur dioxide content An oxidative treatment with manganese dioxide and distillation are needed for the preparation of hydrogena tion-grade hydrogen fluoride [d, 4]... 

A mixture of 300 kilos of toluene and 700 kilos of 65 per cent, sulphuric acid is thoroughly agitated, and 90 kilos of finely powdered manganese dioxide added little by little. The temperature is maintained about 40°. The process is a very slow one, and finally a mixture of unchanged toluene and benzaldehyde is obtained, and from this the sulphite compound is prepared, purified, and the pure benzald,ehyde isolated as usual. 

---