Fluorine preparation

Fluorine prepared in this way is relatively pure. After hydrogen fluoride vapor has been removed by sodium fluoride, one finds that of a sample of the gas in a glass bulb, about 98 per cent is absorbed by mercury. Probably the fluorine is more nearly pure than this would indicate. 

Another successful approach for blocking the intramolecular decomposition illustrated in Fig. 2 involved inhibition of the dehydration step leading to the anhydrohemiketal by replacement of the C-8 proton of erythromycin with fluorine. Preparation of flurithromycin (8-fluoroerythromycin, see Fig. 4) has been achieved by both chemical and biochemical methods. Addition of 8(S)-8-fluoroerythronolide A to a mutant strain of Streptomyces erythreus blocked in biosynthesis of its endogenous lactone (erythronolide) yielded the desired fluorinated erythromycin [40]. This technique of mutasynthesis has been further employed for the production of other fluorinated derivatives of erythromycin [40, 41]. Fluorination of different 8,9-anhydro-6,9-hemiketal derivatives of erythromycin by chemical means with reagents such as trifluoromethyl hypo-fluorite or perchloryl fluoride (with subsequent reduction of the N-oxide) has also been reported [42, 43]. 

After Davy s first calcium preparation the development of alternative methods was limited. At the end of the 19 century, Henri Moissan in France, the discoverer of fluorine, prepared the element by reduction of calcium iodide with potassium. From the beginning of the 20 century, production was based on the electrolysis of fused calcium chloride. 

Kwasnik, W., "Advances in Fluorine Preparation and Electrochemical Fluorination of Inorganic Compounds," Fortschr. Chem. Forsch. 1967,8, 309. 

Siher I) fluoride, AgF, is prepared by evaporation of a solution of excess Ag20 in HF after filtration or by heating anhydrous AgBF. The anhydrous salt is yellow hydrates are known, It is very soluble in water and in many organic solvents. Used as a mild fluorinating agent. On treatment of a solution with Ag a sub-fluoride, Ag2F, is formed. 

Graphite reacts with alkali metals, for example potassium, to form compounds which are non-stoichiometric but which all have limiting compositions (for example K C) in these, the alkaU metal atoms are intercalated between the layers of carbon atoms. In the preparation of fluorine by electrolysis of a molten fluoride with graphite electrodes the solid compound (CF) polycarbon fluoride is formed, with fluorine on each carbon atom, causing puckering of the rings. 

A complete set of trihalides for arsenic, antimony and bismuth can be prepared by the direct combination of the elements although other methods of preparation can sometimes be used. The vigour of the direct combination reaction for a given metal decreases from fluorine to iodine (except in the case of bismuth which does not react readily with fluorine) and for a given halogen, from arsenic to bismuth. 

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 ... 

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... 

Hydrogen fluoride is the most important compound of fluorine. It is prepared in the laboratory, and on the large scale, by the reaction of calcium fluoride with concentrated sulphuric acid. ... 

Fluorine in the free state is too reactive to be of a direct practical value, but it may be used to prepare other compounds of fluorine, which are then used as fluorinating agents, for example chlorine... 

The only important compound is the paramagnetic silver(II) fluoride, AgFj, prepared by fluorination of the metal it is used as a convenient fluorinating agent. 

The reaction of perfluoroalkyl iodides with alkenes affords the perfluoro-alkylated alkyl iodides 931. Q.a-Difluoro-functionalized phosphonates are prepared by the addition of the iododifluoromethylphosphonate (932) at room temperature[778], A one-electron transfer-initiated radical mechanism has been proposed for the addition reaction. Addition to alkynes affords 1-perfluoro-alkyl-2-iodoalkenes (933)[779-781]. The fluorine-containing oxirane 934 is obtained by the reaction of allyl aicohol[782]. Under a CO atmosphere, the carbocarbonylation of the alkenol 935 and the alkynol 937 takes place with perfluoroalkyl iodides to give the fluorine-containing lactones 936 and 938[783]. 

Aryl chlorides and bromides are con veniently prepared by electrophilic aro matic substitution The reaction is lim ited to chlorination and bromination Fluorination is difficult to control lodi nation is too slow to be useful... 

Before sample preparation, surrogate compounds must be added to the matrix. These are used to evaluate the efficiency of recovery of sample for any analytical method. Surrogate standards are often brominated, fluorinated, or isotopically labeled compounds that are not expected to be present in environmental media. If the surrogates are detected by GC/MS within the specified range, it is... 

Fluorine was first produced commercially ca 50 years after its discovery. In the intervening period, fluorine chemistry was restricted to the development of various types of electrolytic cells on a laboratory scale. In World War 11, the demand for uranium hexafluoride [7783-81-5] UF, in the United States and United Kingdom, and chlorine trifluoride [7790-91 -2J, CIF, in Germany, led to the development of commercial fluorine-generating cells. The main use of fluorine in the 1990s is in the production of UF for the nuclear power industry (see Nuclearreactors). However, its use in the preparation of some specialty products and in the surface treatment of polymers is growing. 

Fluorine reacts with high purity carboa or graphite at elevated temperatures uader coatroUed coaditioas to produce fluoriaated carboa, (CF ). Compouads having colors ranging from black to white have beea prepared with fluorine coateats ranging from x = 0.1. o x = 1.3 (70—74). The material... 

An important newer use of fluorine is in the preparation of a polymer surface for adhesives (qv) or coatings (qv). In this apphcation the surfaces of a variety of polymers, eg, EPDM mbber, polyethylene—vinyl acetate foams, and mbber tine scrap, that are difficult or impossible to prepare by other methods are easily and quickly treated. Fluorine surface preparation, unlike wet-chemical surface treatment, does not generate large amounts of hazardous wastes and has been demonstrated to be much more effective than plasma or corona surface treatments. Figure 5 details the commercially available equipment for surface treating plastic components. Equipment to continuously treat fabrics, films, sheet foams, and other web materials is also available. 

High Purity Aluminum Trifluoride. High purity anhydrous aluminum triduoride that is free from oxide impurities can be prepared by reaction of gaseous anhydrous HF and AlCl at 100°C, gradually raising the temperature to 400°C. It can also be prepared by the action of elemental fluorine on metal/metal oxide and subsequent sublimation (12) or the decomposition of ammonium duoroaluminate at 700°C. 

Arsenic pentafluoride can be prepared by reaction of fluorine and arsenic trifluoride or arsenic from the reaction of NF O and As (16) from the reaction of Ca(FS02)2 and H AsO (17) or by reaction of alkaH metal or alkaline-earth metal fluorides or fluorosulfonates with H AsO or H2ASO2F (18). 

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