Oxidising, solvents

Anthracene is oxidised by chromium trioxide, Cr04, to anthraquinone. As the reaction is carried out in solution, a solvent is required which will dissolve both the anthracene and the chromium trioxide, and at the same time be... 

The most widely used cleansing agent is the chromic acid cleaning mixture. It is essentially a mixture of chromic acid (CrOj) and concentrated sulphuric acid, and possesses powerful oxidising and solvent properties. Two methods of preparation are available —... 

Nitrobenzene is an extremely versatile solvent, and may frequently be employed for the crystallisation of compounds which do not dissolve appreciably in the common organic solvents. The vapour is somewhat poisonous, so that recrystaUisations must be carried out in the fume cupboard. After the crystals have been collected, they should be washed with a volatile solvent, such as benzene, alcohol or ether, to remove the excess of nitrobenzene (compare Section 11,32). The only disadvantage of nitrobenzene as a solvent is that it has a pronounced oxidising action at the boihng point. 

Tetrachloroethane is a good solvent for many compounds which dissolve only slightly in the common solvents it is, however, inferior in solvent power to nitrobenzene, but, on the other hand, it does not possess oxidising properties at the boiling point. 

Because they are weak acids or bases, the iadicators may affect the pH of the sample, especially ia the case of a poorly buffered solution. Variations in the ionic strength or solvent composition, or both, also can produce large uncertainties in pH measurements, presumably caused by changes in the equihbria of the indicator species. Specific chemical reactions also may occur between solutes in the sample and the indicator species to produce appreciable pH errors. Examples of such interferences include binding of the indicator forms by proteins and colloidal substances and direct reaction with sample components, eg, oxidising agents and heavy-metal ions. 

The aHphatic iodine derivatives are usually prepared by reaction of an alcohol with hydroiodic acid or phosphoms trHodide by reaction of iodine, an alcohol, and red phosphoms addition of iodine monochloride, monobromide, or iodine to an olefin replacement reaction by heating the chlorine or bromine compound with an alkaH iodide ia a suitable solvent and the reaction of triphenyl phosphite with methyl iodide and an alcohol. The aromatic iodine derivatives are prepared by reacting iodine and the aromatic system with oxidising agents such as nitric acid, filming sulfuric acid, or mercuric oxide. 

Microscopic sheets of amorphous silica have been prepared in the laboratory by either (/) hydrolysis of gaseous SiCl or SiF to form monosilicic acid [10193-36-9] (orthosihcic acid), Si(OH)4, with simultaneous polymerisation in water of the monosilicic acid that is formed (7) (2) freesing of colloidal silica or polysilicic acid (8—10) (J) hydrolysis of HSiCl in ether, followed by solvent evaporation (11) or (4) coagulation of silica in the presence of cationic surfactants (12). Amorphous silica fibers are prepared by drying thin films of sols or oxidising silicon monoxide (13). Hydrated amorphous silica differs in solubility from anhydrous or surface-hydrated amorphous sdica forms (1) in that the former is generally stable up to 60°C, and water is not lost by evaporation at room temperature. Hydrated sdica gel can be prepared by reaction of hydrated sodium siUcate crystals and anhydrous acid, followed by polymerisation of the monosilicic acid that is formed into a dense state (14). This process can result in a water content of approximately one molecule of H2O for each sdanol group present. 

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). 

Chlorates are strong oxidising agents. Dry materials, such as cloth, leather, or paper, contaminated with chlorate may be ignited easily by heat or friction. Extreme care must be taken to ensure that chlorates do not come in contact with heat, organic materials, phosphoms, ammonium compounds, sulfur compounds, oils, greases or waxes, powdered metals, paint, metal salts (especially copper), and solvents. Chlorates should be stored separately from all flammable materials in a cool, dry, fireproof building. 

Cl Vat Blue 4 is prepared from 2-arniaoaiitliraquiQoiie (66) by potash fusion in the presence of an oxidising agent such as sodium nitrite or air. An alternative method by dimerization of 1-aminoanthraquinone (17) by using such solvents as dimethyl sulfoxide or tetramethylurea has been reported, and improved methods for this reaction have been cited (135—138). These methods are considered to be advantageous in terms of the yield as well as the availability of starting compounds. 

Printing of wool or silk with acid dyes is of minor importance. For these fibers the print paste is made with dye solvent, humectant (glycerol and urea), a suitable thickener, and dilute organic acid. An oxidising agent is also added. Fixation follows the procedure for polyamide with fully saturated steam. 

Thiothienoyltrifluoroacetone [4552-64-1] M 228.2, m 61-62". Easily oxidised and has to be purified before use. This may be by recrystd from benzene or by dissolution in pet ether, extraction into IM NaOH soln, acidification of the aqueous phase with 1-6M HCl soln, back extraction into pet ether and final evapn of the solvent. The purity can be checked by TLC. It was stored in ampoules under nitrogen at 0" in the dark. [Muller and Rother Anal Chim Acta 66 49 1973.]... 

The rubber has a very low of -68°C, excellent hydrolytic stability and excellent resistance to ozone, solvents and acids. In addition the rubber does not bum even in an oxidising atmosphere. Although its properties are virtually unchanged in the range -75 to + 120°C it does not possess the heat resistance of other fluoroelastomers. This polymer was marketed by Firestone in the mid-1970s as PNF rubber, but in 1983 the Ethyl Corporation obtained exclusive rights to the Firestone patents and the polymer is now marketed as Eypel F. 

Styrene is a colourless mobile liquid with a pleasant smell when pure but with a disagreeable odour due to traces of aldehydes and ketones if allowed to oxidise by exposure to air. It is a solvent for polystyrene and many synthetic rubbers, including SBR, but has only a very limited mutual solubility in water. Table 16.1 shows some of the principal properties of pure styrene. 

The principal applications of these plastics arose from their very good chemical resistance, as they are resistant to mineral acids, strong alkalis and most common solvents. They were, however, not recommended for use in conjunction with oxidising acids such as fuming nitric acid, fuming sulphuric acid or chlorosulphonic acid, with fluorine or with some chlorinated solvents, particularly at elevated temperatures. 

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