Fluorides special

Trifluoromethylsulphur chloride tetrafluoride, CF3-SF4C1 (which possesses a tronj-octahedral configuration so that all four fluorines attached to sulphur are equivalent), has been prepared by reaction of trifluoromethylsulphur trifluoride with chlorine in the presence of caesium fluoride at room temperature this synthesis is analogous to that of sulphur chloride pentafluoride from sulphur tetrafluoride, chlorine, and caesium fluoride, a method claimed to be inferior to the addition of chlorine monofluoride to sulphur tetrafluoride in the presence of caesium fluoride specially activated by a fusion-solidification-fine-grinding technique. Bis(perfluoroalkyl)-sulphur difluorides result from the fluorination of bis(perfluoroalkyl) sulphides with chlorine monofluoride ... 

Fluorine cannot be prepared directly by chemical methods. It is prepared in the laboratory and on an industrial scale by electrolysis. Two methods are employed (a) using fused potassium hydrogen-fluoride, KHFj, ill a cell heated electrically to 520-570 K or (b) using fused electrolyte, of composition KF HF = 1 2, in a cell at 340-370 K which can be electrically or steam heated. Moissan, who first isolated fluorine in 1886, used a method very similar to (b) and it is this process which is commonly used in the laboratory and on an industrial scale today. There have been many cell designs but the cell is usually made from steel, or a copper-nickel alloy ( Monel metal). Steel or copper cathodes and specially made amorphous carbon anodes (to minimise attack by fluorine) are used. Hydrogen is formed at the cathode and fluorine at the anode, and the hydrogen fluoride content of the fused electrolyte is maintained by passing in... 

Cobalt is a bluish silvery metal, exhibits ferromagnetism, and can exist in more than one crystal form it is used in alloys for special purposes. Chemically it is somewhat similar to iron when heated in air it gives the oxides C03O4 and CoO, but it is less readily attacked by dilute acids. With halogens, the cobalt(II) halides are formed, except that with fluorine the (III) fluoride, C0F3, is obtained. 

L. Holmia, for Stockholm). The special absorption bands of holmium were noticed in 1878 by the Swiss chemists Delafontaine and Soret, who announced the existence of an "Element X." Cleve, of Sweden, later independently discovered the element while working on erbia earth. The element is named after cleve s native city. Holmia, the yellow oxide, was prepared by Homberg in 1911. Holmium occurs in gadolinite, monazite, and in other rare-earth minerals. It is commercially obtained from monazite, occurring in that mineral to the extent of about 0.05%. It has been isolated by the reduction of its anhydrous chloride or fluoride with calcium metal. 

Silyl enol ethers are other ketone or aldehyde enolate equivalents and react with allyl carbonate to give allyl ketones or aldehydes 13,300. The transme-tallation of the 7r-allylpalladium methoxide, formed from allyl alkyl carbonate, with the silyl enol ether 464 forms the palladium enolate 465, which undergoes reductive elimination to afford the allyl ketone or aldehyde 466. For this reaction, neither fluoride anion nor a Lewis acid is necessary for the activation of silyl enol ethers. The reaction also proceed.s with metallic Pd supported on silica by a special method[301j. The ketene silyl acetal 467 derived from esters or lactones also reacts with allyl carbonates, affording allylated esters or lactones by using dppe as a ligand[302]... 

Because hydrogen fluoride is extremely reactive, special materials are necessary for its handling and storage. Glass reacts with HF to produce SiF which leads to pressure buildup and potential mptures. Anhydrous hydrogen fluoride is produced and stored ia mild steel equipment. Teflon or polyethylene are frequently used for aqueous solutions. 

Equipment should be carefiiUy and completely degreased and passivated with low concentrations of fluorine or the gaseous halogen fluoride before use. Special care should be taken that valves are completely disassembled and each part carefiiUy cleaned. 

Arsenic and Boron. Arsenic and boron form volatile fluorides which are difficult to separate from high purity HF. Special equipment and techniques must be used to remove the arsenic. 

In the direct process, NF is produced by the reaction of NH and F2 in the presence of molten ammonium acid fluoride (27). The process uses a specially designed reactor (28). Because H2 is not generated in this process, the ha2ards associated with the reactions between NF and H2 are elirninated. 

Uses. Silver fluoride has found many laboratory and special industrial appHcations. It is used as a soft (nHld) fluorinating agent for selective fluorination (7—17), as a cathode material in batteries (qv) (18), and as an antimicrobial agent (19). Silver fluoride is commercially available from Advance Research Chemicals, Inc., Aldrich Chemicals, Cerac Corp., Johnson/Matthey, PCR, Atochem, and other sources in the United States. The U.S. price of silver fluoride in 1993 was 1000— 1400/kg and the total U.S. consumption was less than 200 kg/yr. 

Fluorocarbons are made commercially also by the electrolysis of hydrocarbons in anhydrous hydrogen fluoride (Simons process) (14). Nickel anodes and nickel or steel cathodes are used. Special porous anodes improve the yields. This method is limited to starting materials that are appreciably soluble in hydrogen fluoride, and is most useflil for manufacturing perfluoroalkyl carboxyflc and sulfonic acids, and tertiary amines. For volatile materials with tittle solubility in hydrofluoric acid, a complementary method that uses porous carbon anodes and HF 2KF electrolyte (Phillips process) is useflil (14). 

Poly(vinyl fluoride) is available from Du Pont both as a resia and as transparent and pigmented films under the trademark Tedlar PVF film. Films are available ia nonoriented and oriented grade ia several tensile modifications and thicknesses, with either adherable or nonadherable release-grade surfaces. The 1992 prices ranged from 30 to 70/kg, vs 24 to 62/kg ia 1988. Prices for specially tailored films were significantly higher. 

The occurrence of pitting seems to stem from the differential stabiUty of the passive film that forms on the titanium alloy. This film does not break down uniformly even when the electrolytes are fluoride and bromide based. The pitting can be so severe that special measures are needed to counteract it. 

Operation and Control. Control of a chromium phosphate conversion coating bath requires monitoring chromium and aluminum concentrations, active fluoride level, and temperature. Coating weight is very sensitive to active, ie, uncomplexed, fluoride. An innovative electrochemical method using a siHcon electrode (25) is employed for measuring active fluoride. A special precaution in chromium phosphate bath operation is the... 

Toluene reacts with carbon monoxide and butene-1 under pressure in the presence of hydrogen fluoride and boron trifluoride to give 4-methyl-j iYbutyrophenone which is reduced to the carbinol and dehydrated to the olefin. The latter is cycHzed and dehydrogenated over a special alumina-supported catalyst to give pure 2,6- dim ethyl n aph th a1 en e, free from isomers. It is also possible to isomerize various dim ethyl n aph th a1 en es to the... 

The vapor-phase conversion of aniline to DPA over a soHd catalyst has been extensively studied (18,22). In general, the catalyst used is pure aluminum oxide or titanium oxide, prepared under special conditions (18). Promoters, such as copper chromite, nickel chloride, phosphoric acid, and ammonium fluoride, have also been recommended. Reaction temperatures are usually from 400 to 500°C. Coke formed on the catalyst is removed occasionally by burning. In this way, conversions of about 35% and yields of 95% have been reported. Carba2ole is frequently a by-product. 

The fluororubbers also form an important class of speciality elastomers and although the market is dominated by the vinylidene fluoride-hexafluoro-propylene copolymers a wide range of materials has been produced over the past 40 years. 

Special procedures apply to certain chemicals, e.g. anhydrous hydrogen fluoride, aqueous hydrofluoric acid, phenol and related compounds)... 

Fire Hazards - Flash Point Not flammable Flammable Umits in Air (%) Not flammable Fire Extinguishing Agents Not pertinent Fire Extinguishing Agems Not To Be Used Not pertinent Special Hazards cf Combustion Products Toxic hydrogen fluoride and cadmium oxide fumes can form Behavior in Fire Not pertinent Ignition Temperature Not pertinent Electrical Hazard Not pertinent Burning Rate Not pertinent. 

Agents Shut off gas source use water to cool adjacent combustibles Fire Extinguishing Agents Not to be Used Data not available Special Hazards of Combustion Products Irritating hydrogen fluoride fumes may form in fire Behavior in Fire Containers may explode. Vapors are heavier than air And may travel a considerable distance Ignition Temperature Data not available Electrical Hazard Data not available Burning Rate Not pertinent. 

Fluorinated polymers stand out sharply against other construction materials for their excellent corrosion resistance and high-temperature stability. In this respect they are not only superior to other plastics but also to platinum, gold, glass, enamel and special alloys. The fluorinated plastics used in process plants are polytetrafluorethylene (PTFE), fluorinated ethylene/ propylene (FEP), polytrifiuoromonochlorethylene (PTFCE) and polyvinyl fluoride (PVF). They are much more expensive than other polymers and so are only economical in special situations [59]. 

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