System potassium fluoride

M. Amadori studied fused mixtures of sodium fluoride and carbonate no compound is formed, and the salts are not miscible in the solid state. There is a eutectic at 690° and 39 mols. per cent, sodium fluoride. Similar results obtain with sodium chloride and carbonate. There is an eutectic at 636° and 59 mols. per cent, of sodium chloride. Similarly, with potassium fluoride and carbonate, there is with a eutectic at 636° and 65 mols. per cent, of potassium chloride. With the system potassium fluoride and carbonate there is a eutectic at 688° with nearly 46 mols. per cent, of potassium fluoride, and another eutectic at 682° with 62 mols. per cent, of potassium fluoride there is a slight rise in the m.p. between the two eutectics, corresponding with the formation of potassium fluorocarbonate, KF.K2C03. 

The coupling of microwave activation and the basic system potassium fluoride/ potassium carbonate was shown to be an efficient method for preparing 2-nitrophenylamines [142] by nudeophihc aromatic substitution. Within few minutes, excellent results were obtained compared with classical heating (Eq. 57) ... 

Pierce, J.W, and H.Y.-P. Hong, 1974, Structural Studies in the System Potassium Fluoride-Yttrium Fluroide, in Kevane, C.J. and T. MoeUer, Proc. Tenth Rare Earth Research Conf., Carefree, AZ, (NTIS, Springfield, VA) 527-37. 

In a caustic scmbbing system, caustic potash, KOH, is preferred to caustic soda, NaOH, because of the higher solubiUty of the resulting potassium fluoride. Adequate solution contact and residence time must be provided in the scmb tower to ensure complete neutralization of the intermediate oxygen difluoride, OF2. Gas residence times of at least one minute and caustic concentrations in excess of 5% are recommended to prevent OF2 emission from the scmb tower. 

Metal halide salts other than sodium iodide have been used sparsely to prepare halodeoxy sugars from sulfonate esters. Lithium chloride (107) and lithium bromide (33) have found limited application. Potassium fluoride (dihydrate) in absolute methanol has been used (51, 52) to introduce fluorine atoms in terminal positions of various D-glucose derivatives. The reaction is conducted in sealed tube systems and requires... 

The residue left from conversion of the chloro to the fluoro compound exploded during distillation at 1.3 mbar [1], Reheating the residue from distillation caused violent decomposition [2], Traces of an aci-nitroquinonoid species (structure str02, p. S1-S7) may have been formed in the chlorodinitrobenzene-potassium fluoride reaction system [3],... 

Some early examples involving microwave-assisted solvent-free Sonogashira couplings using palladium powder doped on alumina/potassium fluoride as catalyst were described by Kabalka and coworkers (Scheme 4.4) [150], In addition, this novel catalytic system has been used in microwave-assisted solvent-free Sonogashira coupling-cyclization of ortho-iodophenol with terminal alkynes, and similarly of ortho-ethynylphenols with aromatic iodides, to generate 2-substituted benzo[b]furans... 

The Levafix P dyes have been replaced by the Levafix PN (DyStar) range, which is based on the 5 chloro-2-fluorO 4-methylpyrimidine system. These two systems are essentially similar, but the Levafix PN dyes have a fluorine atom as the labile entity rather than the methylsulphonyl grouping. The necessary intermediate 5-chloro-2,6-difluoro-4-methyl-pyrimidine (7.25) can be made from 4-methyl-2,5,6-trichloropyrimidine by an exchange reaction with potassium fluoride (Scheme 7.20). Condensation with the dye base (Scheme 7.21) will give a mixture of isomers, namely, the 5 chloro-6-fluoro-4-methyl (7.26) and 5-chloro-2-fluoro-4-methyl (7.27) derivatives. 

Nucleophilic displacement using [ F] fluoride works well in aUphatic systems where reactive haUdes or sulfonates esters can undergo substitution at unhindered sites. In order to introduce a F fluorine atom in a secondary or tertiary position, a two steps strategy was developed. It involves a F-bromofluorination of alkenes, followed by reductive debromination (n-BujSnH, AIBN). [ F]BrF is usually generated in situ from [ F]potassium fluoride and l,3-dibromo-5,5-dimethylhydantoin (DBH) in sulfuric acid. This methodology was successfully applied to label steroids at the 11 and 6a positions [245] (Scheme 60) and to prepare [ F]fluorocyclohexanes [246]. 

The vendor claims that the following metals have been successfully treated to parts per biUion (ppb) and detection limit levels aluminum, arsenic, cadmium, chromium, cobalt, copper, iron, lead, manganese, mercury, molybdenum, nickel, selenium, silver, tin, uranium, vanadium, and zinc. The system is also able to remove ammonia, nitrates, phosphates, potassium, fluorides, and sodium. Studies have also been performed using Aqua-Fix to remove radionuchdes such as uranium from waste streams. 

Properties of the alkali fluorides.—The anhydrous alkali fluorides crystallize in the cubic system.8 Lithium fluoride forms regular optohedrons and nacreous plates sodium fluoride crystallizes in cubes, but in presence of sodium carbonate, the crystals are octohedrons. The cubic crystals are frequently en tremies. H. Schwendenwein has discussed the space lattice of the alkali fluorides, and K. Fajans and H. Grimm estimated the distance of the atoms apart in sodium and potassium fluorides to be respectively 2 34 X 10 8 and 2 67 X10-8 cm. and the respective lattice energies to be 210-4 and 192 2 Cals, per mol. The taste of potassium fluoride is acrid and salty. 

B. Karandeeff found that the fusion curves of the system KF—K2S04 gave eutectics at 883° (41 mols. per cent, of potassium fluoride), and 788° (83 mols. per... 

Substitution of fluorine for halogen in aromatic and alkyl sulfonyl halides can be carried out with or without using a solvent. An aqueous system such as 70 % aqueous potassium fluoride is also used because the rate of hydrolysis is much slower than the rate of fluorination as reported for the conversion of methanesulfonyl chloride (1) to methanesulfonyl fluoride (2).23... 

A general method of introducing the acid fluoride functionality in aryl bromides 12 is their carbonylation under an atmospheric pressure of carbon monoxide in dimethylformamide in the presence of potassium fluoride.33 Several catalytic systems, solvent and the effects of temperature, amount of potassium fluoride used and pressure of carbon monoxide were systematically investigated to find the right conditions to obtain the aroyl fluorides 13. The carbonylation of unactivated aliphatic bromides was unsuccessful. 

This method has been extended to heterocycles bearing a hydroxymethyl-substituted nitrogen. Thus, ethyl l-(hydroxymethyl)pyrazole-4-carboxylate (10) is converted into ethyl 1-(fluoromethyl)pyrazole-4-carboxylate (11) in 76% yield with cesium fluoride/methanesulfonyl fluoride/18-crown-6 system.167 Potassium fluoride did not react at all and tetrabutylammonium fluoride leads to decomposition and formation of coupling products. 

A useful practical method for the preparation of aroyl fluorides 1 and arenesulfonyl fluorides 2 by reaction of the zinc(II) fluoride/pyridine system with the corresponding chlorides has been described.50 Replacement of zinc(II) fluoride by potassium fluoride, or of pyridine by other tertiary amines (Et3N or l-methylpiperidin-2-one) or by other solvents (DMSO, DMF, MeCN, or THF) did not give satisfactory results. The exclusive effectiveness of pyridine is presumably due to its ability to weaken the Zn — F linkage by appropriate coordination to the zinc atom.50... 

A similar reaction was reported by Kabalka et al. where ligandless and solvent-free Suzuki couplings were performed with potassium fluoride on alumina. This reaction is very interesting as the catalyst used was palladium powder, the least expensive form of palladium available32. The authors demonstrated the simplicity of the procedure by efficient isolation of the biaryl products via a simple filtration. This could be done as the palladium catalyst remains adsorbed on the alumina surface. A small amount of water in the matrix was beneficial for the outcome of the reactions. Recycling of the catalyst was possible by adding fresh potassium fluoride to the palladium/alumina surface and the catalytic system remained effective at least through six reaction cycles (Scheme 2.6). 

Stabilized carbon nucleophiles (e.g. from 3-diketones, 3-keto esters, malonate esters, etc.) can be aryl-ated by substitution for chloride on the arene in (Fe(arene)Cp] cation complexes.72-78 81 A base is necessary and two heterogeneous systems are favored potassium carbonate in DMF or potassium fluoride prepared on Celite-545. As usual in the [FeCp]+ system, detachment of the substituted arene requires somewhat extreme conditions, usually pyrolytic sublimation at 200 C.46 An example is given in equation (27). 

All methods that have been used successfully for producing fluorine in quantity are electrochemical and make use of the system hydrogen fluoride-potassium fluoride in different forms of cells and at various temperatures. Cady1 has shown by a study of the freezing points and vapor pressures of this system that there are three regions where electrolysis to produce fluorine is practicable. In each of these regions, the system is liquid, and the vapor pressure of hydrogen fluoride is below atmospheric pressure. 

At low temperature, the electrolyte consists essentially of anhydrous hydrogen fluoride made conducting with dissolved potassium fluoride. Moissan2 first prepared fluorine by the electrolysis of such a solution in the low-temperature range using platinum electrodes. At about 70°C., the system has approximately the composition KF-3HF. The electrolysis of this melt was first described by Lebeau and Damiens3 who employed nickel electrodes. 

The main problem here is removing the phenyl ester groups from the phosphonic moiety.We have found that convenient routes for deblocking are hydrogenation on Adams catalyst and transesterification methods followed by hydrogen bromide in glacial acetic acid treatment. The best results ewre obtained if transesterification was carried out using potassium fluoride-crown ether-methanol system. 

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