Tetrafluoride

Carbon tetrafluoride is formed by passing gaseous fluorine over finely divided carbon (Norit).1 Sugar charcoal especially, and some wood charcoals, give large amounts of higher carbon fluorides and are to be avoided if the lower fluorides are desired. Norit seems to be the best when large yields of carbon tetrafluoride are desired. 

Carbon tetrafluoride is an extremely stable gas at room temperature and hence is suitable for applications calling for a stable gas of higher molecular weight than can be obtained by use of the inexpensive inert gases of the atmosphere. The method of preparation described here gives a product of high purity without attendant explosion hazards such as present themselves in the direct fluorination of carbon. 

The nickel reactor is used to carry out this synthesis. One hundred grams of 30-mesh Carborundum is distributed 

The flow of fluorine is started and as soon as the reaction has commenced, as indicated by heating of the reactor, the fluorine is diluted with an equal volume of dry nitrogen. When a good flow of product is obtained, as evidenced by copious fumes at the exit, the trap is cooled in liquid nitrogen to condense the silicon tetrafluoride and carbon tetrafluoride. The reaction is allowed to continue imtil the 

Carbon tetrafluoride is a colorless, tasteless, and odorless gas when pure but may have a musty odor if contaminated with some of the higher fluorocarbons. It boils at —128 and is inert to hydrolysis of any kind except at temperatures above 1000°. It is inert toward most chemicals although boiling alkali metals and superheated alkali metal vapors attack it slowly. 

TANTALUM(NIOBIUM)(V) FLUORIDB (Tantalum (Niobium) Pentafluoride] 

Submitted by KAREL LUTAR, ANDREJ SMALC, and BORIS 2EMVA Checked by SCOTT A. KINKEADf 

Xenon tetrafluoride was first prepared by heating a gaseous mixture of xenon and fluorine under moderate pressure. However, the product obtained by this method is always contaminated with xenon difluoride and hexafluoride, which are in chemical equilibrium with xenon tetrafluoride. Xenon tetrafluoride obtained in this way can be purified by subsequent chemical purification with arsenic pentafluoride.  

However, pure xenon tetrafluoride can be obtained by thermal dissociation of xenon hexafluoride.  

Xenon reacts with excess fluorine at 300°C under pressure, yielding xenon hexafluoride, which is combined with sodium fluoride to form a nonvolatile complex Na2[XeFg] 

Xenon difluoride and tetrafluoride, which are also present in the reaction mixture, form no complex with sodium fluoride and can be pumped off at room temperature. Finally, Na2[XeFg] is decomposed at 350°C  

Submitted by J. G. Malm and C. L. Chernick Checked by Stanley M. WiLUAMsoNf 

Xenon tetrafluoride has been prepared by a number of methods. Irradiation of a mixture of xenon and fluorine with ultraviolet light produces xenon difluoride if the reaction product is immediately condensed from the gas phase. However, if the di fluoride is allowed to remain in the reaction zone, the tetrafluoride is produced. Passage of an electric discharge through a mixture of xenon and fluorine also produces xenon tetrafluoride. Perhaps the best method is the one in which xenon and fluorine are heated together either in a closed system or in a flow system. The method which uses a closed system allows a somewhat better control of purity and is described below. 

The realtor should be designed to handle 30 atmospheres pressure approximately 4- times the expected pressure), and adequate shielding should be used. Because of the use of fluorine, the procedure should be performed in a good hood. 

Apparatus for preparation and purification of xenon tetrafluoride. A. 30,000-p.s.i. valve, Monel body, Teflon packing. 

The apparatus used for the preparation and purification of xenon tetrafluoride is shown in Fig. 10. The total volume of the manifold including the U-tubes, but excluding all reaction and storage vessels, is about 105 ml. All parts are fabricated of nickel or Monel and are pretreated by 

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Tellurium tetrafluoride, Tep4 m.p. 130 C. Colourless deliquescent solid prepared SeF4 plus TeOj. Hydrolysed by water. 

Vanadium tetrafluoride, VF4. Green solid prepared HF on VCI4. Forms hexa-fluorovanadate(IV) ion (VFa) ". VOF2 formed by hydrolysis. 

Silicon tetrafluoride is formed when hydrogen fluoride reacts with silica or a silicate ... 

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 ... 

Silicon difluoride is obtained as a very reactive gas when silicon tetrafluoride and silicon are heated together. It polymerises rapidly to give (SiF2) , a solid. 

Both selenium hexafluoride and tellurium hexafluoride are more reactive than sulphur hexafluoride. Tellurium hexafluoride is slowly hydrolysed by water to telluric) VI) acid and on heating it decomposes to fluorine and the tetrafluoride. 

The tetrafluorides of the elements can be prepared. They are all less stable than the corresponding hexafluorides and are hydrolysed readily by water. They can all be used as fluorinating agents and sulphur tetrafluoride is extensively used for this purpose, for example the fluorination of organic carbonyl groups ... 

The structure of sulphur tetrafluoride, and probably also SeF and TeF4, is trigonal bipyramidal with one position occupied by a lone pair of electrons ... 

The action of concentrated sulphuric acid liberates hydrogen fluoride, which attacks glass, forming silicon tetrafluoride the latter is hydrolysed to silicic acid by water, which therefore becomes turbid,... 

Survey and account for the group characteristics and trends in the elements of Group O (He-Rn). Outline the preparation and stereochemistry of xenon tetrafluoride. 

L. silex, silicis, flint) Davy in 1800 thought silica to be a compound and not an element later in 1811, Gay Lussac and Thenard probably prepared impure amorphous silicon by heating potassium with silicon tetrafluoride. 

We also developed a number of other useful new fluorinating reagents. They ineluded a convenient in situ form of sulfur tetrafluoride in pyridinium polyhydrogen fluoride, selenium tetrafluoride, and ey-anurie fluoride. We introdueed uranium hexafluoride (UFg), depleted from the U-235 isotope, which is an abundant by-product of enrichment plants, as an effective fluorinating agent. 

Representing a two electron covalent bond by a dash (—) the Lewis structures for hydrogen fluoride fluorine methane and carbon tetrafluoride become... 

IV) oxide sulfate (III) sulfate (III) sulfide Xenon difluoride hexafluoride tetrafluoride trioxide Ytterbium... 

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