Of manganese

Manufactured by the liquid-phase oxidation of ethanal at 60 C by oxygen or air under pressure in the presence of manganese(ii) ethanoate, the latter preventing the formation of perelhanoic acid. Another important route is the liquid-phase oxidation of butane by air at 50 atm. and 150-250 C in the presence of a metal ethanoate. Some ethanoic acid is produced by the catalytic oxidation of ethanol. Fermentation processes are used only for the production of vinegar. 

Koretsky G M and Knickelbein M B 1997 Photoionization studies of manganese oiusters ionization potentiais for Mn-,to Mn, J. Chem. Phys. 106 9810... 

The following redox potentials are given for the oxidation of manganese(II) to manganese(III) in acid and alkaline solution. 

The "periodic acids and periodates are powerful oxidising agents and they will oxidise manganese to manganate(VlI). a reaction used to determine small quantities of manganese in steel. 

Fused potassium nitrate is a powerful oxidising agent (cf. the oxidation of manganese compounds, p.. IS6 ... 

Manganese(IV) oxide is the only familiar example of this oxidation state. It occurs naturally as pyrolusite, but can be prepared in an anhydrous form by strong heating of manganese(II) nitrate ... 

However the Mn (aq) ion can be stabilised by using acid solutions or by complex formation it can be prepared by electrolytic oxidation of manganese(II) solutions. The alum CaMn(S04)2.12H2O contains... 

The complexes of manganese(III) include [Mn(CN)g] (formed when manganesefll) salts are oxidised in presence of cyanide ions), and [Mnp5(H20)] , formed when a manganese(II) salt is oxidised by a manganate(VII) in presence of hydrofluoric acid ... 

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. 

Manganese minerals are widely distributed oxides, silicates, and carbonates are the most common. The discovery of large quantities of manganese nodules on the floor of the oceans may become a source of manganese. These nodules contain about 24% manganese together with many other elements in lesser abundance. 

Potassium permanganate (KMn04) will also oxidize pri mary alcohols to carboxylic acids What is the oxidation state of manganese in KMn04 ... 

Sodium bismuthate (oxidation of manganese) heat 20 parts of NaOH nearly to redness in an iron or nickel crucible, and add slowly 10 parts of basic bismuth nitrate which has been previously dried. Add 2 parts of sodium peroxide, and pour the brownish-yellow fused mass on an iron plate to cool. When cold break up in a mortar, extract with water, and collect on an asbestos filter. 

Fig. 4.18 Plot of log (.x/(mg g" )) against log (p°/p) for the adsorption of nitrogen at 77 K on the samples of manganese dioxide referred to in Fig. 4.16. Outgassing temperature (A) room (B) 393 K (C)443 K (D) 493 K. For the points denoted by V in Curve A, a sample was outgassed at 493 K and charged with nonane before the final outgassing at room temperature. (Courtesy Lee and Newnham.)...

An additional problem is encountered when the isolated solid is non-stoichiometric. For example, precipitating Mn + as Mn(OH)2, followed by heating to produce the oxide, frequently produces a solid with a stoichiometry of MnO ) where x varies between 1 and 2. In this case the nonstoichiometric product results from the formation of a mixture of several oxides that differ in the oxidation state of manganese. Other nonstoichiometric compounds form as a result of lattice defects in the crystal structure. ... 

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. 

Various ways of overcoming the PTA oxidation problem have been incorporated into commercial processes. The predominant solution is the use of high concentrations of manganese and cobalt ions (2,248—254), optionally with various cocatalysts (204,255,256), in the presence of an organic or inorganic bromide promoter in acetic acid solvent. Operational temperatures are rather high (ca 200°C). A lesser but significant alternative involves isolation of intermediate PTA, conversion to methyl/)-toluate, and recycle to the reactor. The ester is oxidized to monomethyl terephthalate, which is subsequentiy converted to DMT and purified by distillation (248,257—264). 

Tables 1 and 2, respectively, Hst the properties of manganese and its aHotropic forms. The a- and P-forms are brittle. The ductile y-form is unstable and quickly reverses to the a-form unless it is kept at low temperature. This form when quenched shows tensile strength 500 MPa (72,500 psi), yield strength 250 MPa (34,800 psi), elongation 40%, hardness 35 Rockwell C (see Hardness). The y-phase may be stabilized usiag small amounts of copper and nickel. Additional compilations of properties and phase diagrams are given ia References 1 and 2.

None of the natural sulfides of manganese are of any commercial importance. Some siUcates have been mined. Rhodonite and braunite are of iaterest because these are frequendy associated with the oxide and carbonate minerals. The chemical composition of some common manganese minerals are given ia Table 3. 

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