Fluorine compounds carbon tetrafluoride

Nonmetals, such as sulfur, phosphorus and carbon (amorphous) inflame in fluorine forming their corresponding fluoro compounds, such as sulfur hexafluoride (SFe), phosphorus pentafluoride (PF5), and carbon tetrafluoride (CF4). 

Carbon fluoride [also known as carbon monofluoride, polycarbon monofluoride, graphite fluoride, or (CFx)n] is a solid, layered, non-stoichiometric fluorocarbon of empirical formula CFX, where 0 < x < 1.25, obtained by the action of elemental fluorine on carbon. Fluorine combines with carbon and yields three solid compounds CFX, C2FX, and C4FX as well as varying amounts of volatile fluorocarbons as byproducts. With appropriate selection of fluorination conditions nearly 100% conversion of carbon to carbon tetrafluoride can occur. 

Increasing the number of hydroxy groups in the substrate results in a sharp decrease in the yield of fluorinated compounds due to resinification and carbonization. This may be avoided by conducting the reactions at low temperatures in anhydrous hydrogen fluoride. Thus, the reaction of sulfur tetrafluoride with propane-1.2,3-triol (glycerol) at — 40 C gives 3-fluoro-propane-l,2-diyl sulfite (5) in high yield.60... 

Since the time of the earliest work concerned with the reaction of hydrocarbons and fluorine in 1890 by Moissan (who isolated fluorine in 1886), numerous difficulties have been reported. According to Lovelace et al the action of fluorine on a carbon compound can be likened to a combustion process where the products are carbon tetrafluoride and hydrogen fluoride (1). 

The interaction of fluorine with an organic compound liberates a quantity of energy which is frequently of the order of magnitude of, or greater than, the energy which binds the carbon atoms in chains. It is estimated 63 that the addition of fluorine to a double bond liberates ldS calories per mole, whereas chlorine liberates only 30 calories. Careful control qf the temperature throughout the reacting masses is therefore essential. Even in the most favorable cases, much decomposition occurs and carbon tetrafluoride is frequently the main reaction product.62-6 ... 

Carbon tetrafluoride, CF4, mp — 185 °C, bp — 128 °C, which is the end product of the fluorination of carbon compounds, is a very stable gas. It can also be made by the fluorination of silicon carbide (equation 3). The SiF4 is removed from the CF4 by passing the product gases through 20% aqueous NaOH, which removes the SiF4 as soluble sodium silicate but leaves the CF4 unaffected. This major difference in hydrolytic reactivity of CF4 and SiF4 is a consequence of accessible d orbitals on silicon but not on carbon. 

It is unfortunate that there are no other simple organic compounds of fluorine for which AHf is known. Some indication may, however, be obtained from j3-fluoroethanol GH2F. GH2OH, the heat of formation of which has been determined by combustion. From this we deduce (G-F)=95 kcal, in agreement with the value obtained from the lower heat of atomization of carbon tetrafluoride. This is not completely certain, however, since the heat of formation of this compound may not be reliably known. Nevertheless, under the circumstances we must prefer (G-F) = 94 kcal. 

High-purity nitrogen oxide trifluoride has been obtained by fluorolysis of the nickel salt. By first forming this compound, troublesome impurities such as carbon tetrafluoride (from the fluorine) and nitrous oxide (from the nitric oxide) are avoided. The mixture, with nitrosyl fluoride and some nitryl fluoride, is purified chemically by titrating the gas with boron trifluoride, when both of the strongly basic oxyfluorides are removed as fluoroborates ... 

Carbon tetrafluoride is an extraordinarily stable compound. It is the end product in the fluorination of any carbon-containing compound. A useful laboratory preparation, for example, involves the fluorination of silicon carbide. The SiF4 also formed is removed easily by passing the mixture through 20% NaOH solution. The CF4 is unaffected, whereas the SiF4 is immediately hydrolyzed the difference is due to the fact that, in CF4, carbon is coordinately saturated whereas silicon in SiF4 has 3d orbitals available for coordination of OH- ions in the first step of the hydrolysis reaction. 

In one approach" " thin-film aluminum is vapor deposited or sputtered onto the silicon wafer and photoetched to form a mask to etch the vias. The vias are plasma etched using fluorine or a gaseous fluoride compound such as carbon tetrafluoride but etching is stopped short of going completely through the silicon. The aluminum mask is then removed and silicon dioxide is deposited over the entire wafer to isolate the silicon from subsequent deposition of copper. A tie layer of Ti/W is generally deposited prior to copper deposition. The vias are then filled with either a conductive... 

C Fj-NFa), trifluoromethyliminosulphur diiluoride [- - CFj-NFa, (CFa)2NF], pentafluoroethyliminosulphur difluoride CaFs NFa), cyanuric fluoride CFs-NF, (CFa)jNF], thiocyanuric acid [-< CFj-NFj, (CF8)aNF], melamine [- CF3 NF2, (CFs)aNF, CFa(NFa)a], methyl thiocyanate (-> CFa NFj), and methyl isothiocyanate CFs-NFa) carbon tetra-fluoride and nitrogen trifluoride were the major products from these fluorina-tions, and a study has been made of the production of the latter via electrochemical fluorination of urea and related compounds. Details of the production of AtALdifiuorotrifluoromethylamine via injection of carbon tetrafluoride into a nitrogen plasma at 1500—6000 K and direct fluorination of potassium cyanide" have appeared in the patent literature preparation of this difluoroamine by u.v. irradiation of a mbcture of hexafluoro-acetone and tetrafluorohydrazine has also been described, and the new compounds CFCla-NFa, CClj-NFg, and ClS-CCIj-NF, have been obtained by photolysis of the hydrazine in the presence of thiocarbonyl chloride. ... 

An improved method of synthesis of fluoroxypentafluoroselenium SeFs-OF has been developed, viz. direct fluorination of the solid (KSeOFj ) formed by the addition of potassium fluoride to seleninyl fluoride. Treatment of the fluoroxy-compound with perfluorocyclopentene, carbon monoxide, and sulphur tetrafluoride has yielded the new compounds cyclo-CsF -O-SeF, SeFs O COF, and SeFs-O SFj, respectively. 

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