Tetrafluoride reactions

Thionyl fluoride, as by-product in sulfur tetrafluoride reactions, 41, 105 toxidty of, 41,105 Thiophene-2-OL, 43, 55 2(5H)-Thiophenone, 43, 55 Thiosemicarbazide, in synthesis of 1,2,4 triazole, 40, 99 reaction with formic acid to yield l-formyl-3-thiosemicarbazide, 40,99... 

Silicon tetrafluoride is a colourless gas, b.p. 203 K, the molecule having, like the tetrahalides of carbon, a tetrahedral covalent structure. It reacts with water to form hydrated silica (silica gel, see p. 186) and hexafluorosilicic acid, the latter product being obtained by a reaction between the hydrogen fluoride produced and excess silicon tetrafluoride ... 

Tin reacts completely with fluorine above 190°C to form tin tetrafluoride [7783-62-2] SnF. Titanium reacts appreciably above 150°C at a rate dependent on the size of the particles the conversion to titanium tetrafluoride [7783-63-3] TiF, is complete above 200°C. Fluorine reacts with zirconium metal above 190°C. However, the formation of a coating of zirconium tetrafluoride [7783-64 ] ZrF, prevents complete conversion, the reaction reaching... 

Nonmeta.ls, Sulfur reacts with fluorine to yield the remarkably stable sulfur hexafluoride, SF. Operating conditions must be controlled because a mixture of the lower fluorides such as disulfur difluoride [13709-35-8] 2 2 disulfur decafluoride [5714-22-7] 2 10 sulfur tetrafluoride [7783-60-0] SF4, may also be formed. When this reaction is carried out between 310 and 340°C, SF is primarily obtained and essentially no SF and only trace amounts of lower fluorides. Below 300°C, and preferably at ca 275°C, SF is the primary product. At 450—500°C, a mixture comprising ca 50% SF and the lower sulfur fluorides is formed (see Fluorine compounds, inorganic-sulfur). 

Carbon and Graphite. Fluorine reacts with amorphous forms of carbon, such as wood charcoal, to form carbon tetrafluoride [75-73-0], CF, and small amounts of other perfluorocarbons. The reaction initiates at ambient conditions, but proceeds to elevated temperatures as the charcoal bums ia fluoriae. 

Sulfur tetrafluoride [7783-60-0] SF, replaces halogen in haloalkanes, haloalkenes, and aryl chlorides, but is only effective (even at elevated temperatures) in the presence of a Lewis acid catalyst. The reagent is most often used in the replacement of carbonyl oxygen with fluorine (15,16). Aldehydes and ketones react readily, particularly if no alpha-hydrogen atoms are present (eg, benzal fluoride [455-31-2] from benzaldehyde), but acids, esters, acid chlorides, and anhydrides are very sluggish. However, these reactions can be catalyzed by Lewis acids (HP, BF, etc). 

Initial attempts at reactions between fluorine and hydrocarbons were described as similar to combustion and the reaction products contained mostly carbon tetrafluoride and hydrogen fluoride ... 

Depending on the ring substituent, trifluoromethoxyben2enes can be made by the sequential chlorination—fluorination of anisole(s) (351—354). A one-step process with commercial potential is the BF (or SbF2)-cataly2ed reaction of phenol with carbon tetrachloride/hydrogen fluoride (355). Aryl trifluoromethyl ethers, which may not be accessible by the above routes,may be made by fluorination of aryl fluoroformates or aryl chlorothioformates with sulfur tetrafluoride (348) or molybdenum hexafluoride (356). 

Tetrafluoroethylene undergoes addition reactions typical of an olefin. It bums in air to form carbon tetrafluoride, carbonyl fluoride, and carbon dioxide (24). Under controlled conditions, oxygenation produces an epoxide (25) or an explosive polymeric peroxide (24). Trifluorovinyl ethers,... 

An alternative route of manufacture is from siUcon tetrafluoride that is generated ia large quantities as a by-product of the production of phosphate fertilizers. The reaction is... 

Sihcon hahdes can be easily prepared by the reaction of sihcon or sihcon alloys and the respective halogens (24). Fluorine and sihcon react at room temperature to produce sihcon tetrafluoride. Chlorine reacts with sihcon exothermahy, but the mixture must be heated to several hundred degrees centigrade to initiate the reaction (25). Bromine and iodine react with sihcon at red heat. 

The temperature is chosen to maximize reaction rate and to avoid the competitive formation of the tetrafluoride. Alternative preparation methods include the reaction between TiCl and gaseous HF,... 

Titanium Tetrafluoride. Titanium tetrafluoride [7783-63-3] is a white hygroscopic soHd, density 2798 kg/m, that sublimes at 284°C. The properties suggest that it is a fluorine-bridged polymer in which the titanium is six-coordinate. The preferred method of preparation is by direct fluorination of titanium sponge at 200°C in a flow system. At this temperature, the product is sufficiently volatile that it does not protect the unreacted sponge and the reaction proceeds to completion. The reaction of titanium tetrachloride with cooled, anhydrous, Hquid hydrogen fluoride may be used if pure hydrogen fluoride is available. 

A patent (122) for the production of pigment-grade titanium dioxide describes preparation of titanium tetrafluoride by the reaction of SiF and ilmenite. 

Reduction of uranium tetrafluoride by magnesium metal has been described in detail (40,53). It is often referred to as the Ames process, since it was demonstrated at the Ames Laboratory in early 1942. The reaction is very exothermic and the reduction process is carried out in a sealed bomb due to... 

The use of potassium hexafluorosihcate is preferred over sodium hexafluorosihcate because of the lower tendency of the potassium compound to dissociate the lose sihcon tetrafluoride by sublimation. The addition of potassium carbonate or chloride to the fusion mix further reduces this tendency and promotes completion of the reaction. The reaction is conducted in a rotary furnace operating at 700°C. The product is cmshed prior to leaching with acidified hot water. The hot slurry is filtered to remove the sihca, and potassium hexafluorozirconate crystallizes as the solution cools. 

Reaction of Carbonyl Compounds with Sulfur Tetrafluoride... 

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