Preparation of Oxygen

On a laboratory scale, O2 can be prepared by decomposition of certain oxygen-containing compounds. Heavy metal oxides, such as HgO, are not thermally stable and are fairly easily decomposed  

Finally, the usual general chemistry experiment for the preparation of oxygen involves the decomposition of KCIO3  

This reaction is very complex, with part of the Mn02 catalyst being converted to the permanganate, KMn04, which then decomposes  

Eventually, the manganate also decomposes so that Mn02 is regenerated in the end. 

The process is considerably more complicated than the straightforward decomposition of KC103. 

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On the industrial scale oxygen is obtained by the fractional distillation of air. A common laboratory method for the preparation of oxygen is by the decomposition of hydrogen peroxide. H Oj, a reaction catalysed by manganese(IV) oxide ... 

IV) oxide, the latter being used in the eommon laboratory preparation of oxygen from hydrogen peroxide (p. 260. ... 

The superacid-catalyzed electrophile oxygenation of saturated hydrocarbons, including methane with hydrogen peroxide (via H302 ) or ozone (via HOs ), allowed the efficient preparation of oxygenated derivatives. 

A catalyst is a substance that speeds up a chemical reaction without undergoing a permanent change in its own composition. Catalysts are often but not always noted above or below the arrow in the chemical equation. Since a small quantity of catalyst is sufficient to cause a large quantity of reaction, the amount of catalyst need not be specified it is not balanced like the reactants and products. In this manner, the equation for a common laboratory preparation of oxygen is written... 

Many metal sulfides when mixed intimately with metal halogenates form heat-, impact- or friction-sensitive explosive mixtures [1], That with antimony trisulfide can be initiated by a spark [2] and with silver sulfide a violent reaction occurs on heating [3], For the preparation of oxygen mixture , antimony trisulfide was used in error instead of manganese dioxide, and dining grinding, the mixture of sulfide and chlorate exploded very violently [4],... 

Reaction with water is vigorous, and with large amounts of peroxide it may be explosive. Contact of the peroxide with combustibles and traces of water may cause ignition [1], Violent explosions on two occasions during attempted preparation of oxygen were attributed to traces of sodium in the peroxide. The former would liberate hydrogen and ignite the detonable mixture [2,3],... 

The halic acids may not be industrially important, but their salts certainly are. Sodium chlorate is produced in enormous quantities and used in processes in which its oxidizing strength makes it a versatile bleach. One such use is in making paper, and potassium chlorate is used as the oxidizing agent in matches. The decomposition of potassium chlorate was discussed in Chapter 13 in connection with the laboratory preparation of oxygen. 

The preparation of oxygen substituted porphyrazines as analogues to the thiol appended porphyrazines proved to be a formidable challenge. Unlike the sulfur appended porphyrazines for which Na2(mnt) was a readily available precursor, no simple dinitrile precursor could be prepared for the analogous oxygen systems. In 1997, this hurdle was overcome through the preparation of a chiral dispiroketal appended pz (11), which could be further deprotected to form the diol and then either peripherally metalated or converted to the pyridazine (10). These oxygen appended porphyrazines are described in Section VI. 

Table 3.20 lists examples of the preparation of oxygen-containing heterocycles by RCM. Further examples, including lactones [895], pyrans [896,897], chromenes [839], tetrahydrofurans [838], phosphonates [898], and oxepines [856,899-902], have been reported. For references to macrocyclizations see Scope and Limitations in this section. 

Scheme 13.15 Preparation of oxygen-substituted VCPs 142 (Eq. 1) and 163 (Eq. 2). Conditions (a) Na metal, TMSCI, Et20, A (b) MeOH, RT (c) vinylmagnesium bromide, EtjO, 0°C to RT (d) TBSOTf, 2,6-lutidine, CHjCb, RT (e) N-bromo-succinimide, 2-methoxyethanol, -78 °C to RT (f) KOH, RT to 90°C (g) 1.3 equiv. CH2I2, Zn metal, CuCI, AcCI, EtjO, A.

Early preparation of oxygen involved thermal dissociation of metal oxides, notably mercury(II) oxide, which was used independently by both Priestley... 

Potassium chlorate is an oxidizing agent in matches, fireworks and explosives. The head of safety matches is coated with potassium chlorate which is struck on a surface consisting of red phosphorus, antimony(lII) sulfide and an adhesive to light the fire. It also is used in laboratory preparation of oxygen. Its dilute aqueous solution is an antiseptic. 

Potassium chlorate decomposes on heating below its melting point and in the presence of a catalyst, forming potassium chloride and oxygen. The reaction is catalyzed by manganese dioxide and is used in laboratory preparation of oxygen ... 

Cs2BkCl6 is not isomorphous with Cs2PuCl6 or CsaCeCU 408 this compound would provide a useful starting material for the preparation of oxygen donor complexes of BkCLt, which are at present unknown, by the methods used to prepare PuCU complexes of this type (p. 1161). 

An unusual new synthesis method involves carrying out reactions in a molten salt medium, and has been used on an industrial scale for the production of metallic nitride, carbide or carbonitride powders.25 An illustration of this CEREX process is the preparation of oxygen-free titanium nitride in molten calcium chloride. The method involves the reaction between titanium tetrachloride and calcium nitride ... 

This method is applied in practice only to the preparation of oxygen, and of chlorine, bromine, and iodine but many other elements may be thus made, where the compound heated does not tend to re-form on cooling. These cases will be considered first. 

The residual liquid in consequence becomes increasingly richer m oxygen as evaporation proceeds. This has been made the basis of a very successful commercial method for the preparation of oxygen.1... 

Boussmgault attempted to use the foregoing reactions for the preparation of oxygen oil a commercial scale, but found that after several reheatings the barium oxide lost its power of absorbing oxygen. This difficulty was eventually overcome by the brothers Brin,3 who formed a company for the preparation of oxygen for industrial purposes.4... 

II is important to remember that commercial manganese dioxide is occasionally contaminated with carbonaceous material such as coal dust. Such a mixture is very liable to explode when heated with potassium chlorate owing to the rapid combustion of the carbon m the oxygen. Manganese dioxide should, therefore, always be tested beforehand and rejected for the preparation of oxygen if it is found to contain any carbonaceous matter. 

This process is us d commercially, not for the preparation of oxygen, hut for pro paring a mixture of sulphur cUnxUle and oxygen in the requisite proportions to yield sulphur trloxide,... 

The foregoing reactions were made the basis of a commercial method for the preparation of oxygen from the air, but, owing to the short life of the solid phase, the process has not proved particularly successful.4... 

Although a higher temperature is required for the preparation of oxygen by this method than is the ease with barium peroxide (set p. 10), the calcium plumbate is more rapidly regenerated in the presence of air when the temperature is lowered furthermore, il is not necessary to remove the carbon dioxide from the air as in Brin s process. 

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