Manganese dioxide oxidation temperature

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. 

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... 

The oxidation of organic compounds by manganese dioxide has recently been reviewed. It is of limited application for the introduction of double bonds, but the advantages of mildness and simple workup make it attractive for some laboratory-scale transformations. Manganese dioxide is similar to chloranil in that it will oxidize A -3-ketones to A -dienones in refluxing benzene. Unfortunately, this reaction does not normally go to completion, and the separation of product from starting material is difficult. However, Sondheimer found that A -3-alcohols are converted into A -3-ketones, and in this instance separation is easier, but conversions are only 30%. (cf. Harrison s report that manganese dioxide in DMF or pyridine at room temperature very slowly converts A -3-alcohols to A -3-ketones.)... 

Oxidation of di-n-butyl sulphide with activated manganese dioxide in light petroleum gave di-n-butyl sulphoxide exclusively126. However, the reaction was very slow at room temperature. This reagent is also suitable for oxidation of diallyl sulphides although, after 76 h, diallyl sulphoxide was isolated in 13% yield only. 

Electrophilic aromatic substitution of the arylamine 780a using the iron-complex salt 602 afforded the iron-complex 785. Oxidative cyclization of complex 785 in toluene at room temperature with very active manganese dioxide afforded carbazomycin A (260) in 25% yield, along with the tricarbonyliron-complexed 4b,8a-dihydro-3H-carbazol-3-one (786) (17% yield). The quinone imine 786 was also converted to carbazomycin A (260) by a sequence of demetalation and O-methylation (Scheme 5.86). The synthesis via the iron-mediated arylamine cyclization provides carbazomycin A (260) in two steps and 21% overall yield based on 602 (607-609) (Scheme 5.86). 

Selective oxidation of the iron complex 785 with commercial manganese dioxide in dichloromethane at room temperature afforded the iron-complexed... 

Manganese(II) oxide is obtained commercially from manganeseflV) oxide (manganese dioxide) by the reduction with hydrogen, carbon monoxide or methane at elevated temperatures (>800°C) ... 

The pyrimidine synthesis was therefore changed to the alkynyl ketone route as the appropriate precursors could be formed under much milder conditions. Thus, treatment of the chloro aldehyde 1002 with ethynyl Grignards or lithium species at low temperature, followed by mild oxidation with manganese dioxide, gave the desired chloro alkynyl ketones 1003, which could be successfully converted to the pyrimidine products 1004, by condensation with substituted guanidines, without displacement of the chlorine atom <2003X9001, 2005BMC5346>. 

Other reported syntheses include the Reimer-Tiemann reaction, in which carbon tetrachloride is condensed with phenol in the presence of potassium hydroxide. A mixture of the ortho- and para-isomers is obtained the para-isomer predominates. -Hydroxybenzoic acid can be synthesized from phenol, carbon monoxide, and an alkali carbonate (52). It can also be obtained by heating alkali salts of -cresol at high temperatures (260—270°C) over metallic oxides, eg, lead dioxide, manganese dioxide, iron oxide, or copper oxide, or with mixed alkali and a copper catalyst (53). Heating potassium salicylate at 240°C for 1—1.5 h results in a 70—80% yield of -hydroxybenzoic acid (54). When the dipotassium salt of salicylic acid is heated in an atmosphere of carbon dioxide, an almost complete conversion to -hydroxybenzoic acid results. They>-aminobenzoic acid can be converted to the diazo acid with nitrous acid followed by hydrolysis. Finally, the sulfo- and halogenobenzoic acids can be fused with alkali. 

Native urine should be protected from light and stored at -20°C until processed. Oxidized urine sample can be stored at room temperature, but light protection is still recommended. Two procedures for the oxidation of urine (and other samples) are used (1) oxidation with manganese dioxide (Mn02) under acidic conditions, and (2) oxidation with iodine (iodine/potassium iodide, I2/KI) under acidic and basic conditions. The Mn02 oxidation method is a routine method used to quantify total pterins (fully oxidized neopterin, monapterin, biopterin, primapterin, isoxanthopterin, and pterin) the I2/KI method is used according to Fukushima and Nixon [11] for the differential oxidation of pterins and quantification of BH4. Total biopterin represents the sum of BH4, BH2, and fully oxidized biopterin. Under acidic conditions BH4 and BH2 are oxidized to biopterin, while under basic conditions only BH2 is oxidized to... 

The necessary oxygen need not be obtained from the air. Sulphur dioxide is readily obtained by heating sulphur with certain oxides, dioxides or peroxides. Sulphur vapour and steam heated at a suitable temperature in the presence of iron oxide, as catalyst react to form sulphur dioxide and hydrogen which may be recovered separately. With manganese dioxide and powdered sulphur the reaction proceeds as follows ... 

The manufacture of secondary batteries based on aqueous electrolytes forms a major part of the world electrochemical industry. Of this sector, the lead-acid system (and in particular SLI power sources), as described in the last chapter, is by far the most important component, but secondary alkaline cells form a significant and distinct commercial market. They are more expensive, but are particularly suited for consumer products which have relatively low capacity requirements. They are also used where good low temperature characteristics, robustness and low maintenance are important, such as in aircraft applications. Until recently the secondary alkaline industry has been dominated by the cadmium-nickel oxide ( nickel-cadmium ) cell, but two new systems are making major inroads, and may eventually displace the cadmium-nickel oxide cell - at least in the sealed cell market. These are the so-called nickel-metal hydride cell and the rechargeable zinc-manganese dioxide cell. There are also a group of important but more specialized alkaline cell systems which are in use or are under further development for traction, submarine and other applications. 

Manganese dioxide very soon became a widely used standard oxidant for the transformation of allylic and benzylic alcohols into aldehydes and ketones.4 It offers very mild conditions and is extremely selective for allylic and benzylic alcohols when it is not employed at a high temperature. On the other hand, the work-up of oxidations with M11O2 is very simple, involving just filtration of suspended solid and elimination of solvent. 

Some commercial samples of precipitated manganese dioxide may be active enough for use directly in an oxidation process. To assess the activity of a sample of manganese dioxide, dissolve 0.25 g of pure cinnamyl alcohol in 50 ml of dry light petroleum (b.p. 40-60 °C) and shake the solution at room temperature for 2 hours with 2g of the sample of manganese dioxide (previously dried over phosphoric oxide). Filter, remove the solvent by evaporation and treat the residue with an excess of 2,4-dinitrophenylhydrazine sulphate in methanolt (Section 9.6.13, p. 1257). Collect the cinnamaldehyde 2,4-dinitrophenyl-hydrazone and crystallise it from ethyl acetate. An active dioxide should give a yield of the derivative, m.p. 255 °C (decomp.), in excess of 0.35 g (60%). 

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