Potassium fluoride, and

Grind finely pure laboratory grade, anhydrous potassium fluoride, and heat it in an electrically heated oven at 180-210° store in a desiccator. Before use, dry the powdered salt at 180° for 3 hours and grind again in a warm (ca. 50°) glass mortar. 

Lead Fluoride. Lead difluoiide, Pbp2, is a white oithorhombic salt to about 220°C where it is transformed into the cubic form some physical properties ate given in Table 1. Lead fluoride is soluble in nitric acid and insoluble in acetone and ammonia. It is formed by the action of hydrofluoric acid on lead hydroxide or carbonate, or by the reaction between potassium fluoride and lead nitrate. 

Stenc effects are presumably also responsible for the surprising formation of a chlorinated product from reaction of a hindered fluorinated olefin with potassium fluoride and iodine chloride [U6] (equation 18). 

Tetrakis(trifluoromethyl)dithietane is generated by dimerization of hexa-fluorothioaeetone which is prepared in situ from hexafluoiopropylene with potassium fluoride and sulfur [189] or with sulfur and antimony pentafluoride [190] (equation 27)... 

Polymer-supported tetraphenylphosphonium bromide is a recyclable catalyst for halogen-exchange reactions. The reaction of 1 equivalent of chloro-2,4-dinitrobenzene with 1 5 equivalents of spray-dned potassium fluoride and 0.1 equivalent of this catalyst in acetonitnle at 80 C for 12 h gives 2,4-dinitro-fluorobenzene m 98% yield An 11% yield is obtained without the catalyst [3 /]. 

The conversion of octachloronaphthalene to octafluoronaphthalene with potassium fluoride and either 18-crown-6, dibenzo-18-crown-6, cis,j>m,cis-dicyclohexano-18-crown-6, cis,anti,cis-dicyclohexano-l 8-crown-6, or irons,syn,trails-dicyclohexano-18-crown-6 demonstrates that 18-crown-6 or dibenzo-18-crown-5 increases the yield and selecuvity and decreases the reaction time [55] Treatment of 3,4-dichloro-],2,5-thiadiazole with potassium fluonde in sulfolane with and without 18-crown-6 present shows that less severe conditions can be used with either 18-crown-6 or dibenzo-18-crown-6 to form 3,4-difluoro-l,2,5-thiadiazole (equation 34)... 

Polyethylene glycol (molecular weight, 300-6(W) can aid in the displacement of activated halogen by fluorine. Propionyl chloride is converted to propionyl fluoride with potassium fluoride and polyethylene glycol in acetonitrile [63] Treatment of benzyl chloride with a mixture of potassium fluoride and potassium iodide for 5 h in acetonitrile containing polyethylene glycol 200 gives benzyl fluoride in 62% yield [64],... 

Alkanoyl chlorides and chloroformates can be treated with potassium fluoride and benzyItriethylammonium chloride to obtain the respective alkanoyl fluorides or fluoroformates [62]. 2-Amino-6-chloro-9-(2,3,5-tri-0-acetyl-P-D-ribofurano-syl)purine is converted to the 2-amino-6-fluoro product with potassium fluoride and trimethylamme in dimethylformamide under rigorously anhydrous conditions [65] (equation 37)... 

Tetrasubstituted phosphonium halides are just as effective as their ammonium counterparts. A combination of tetraphenylphosphonium bromide and either 18-crown-6 or polyethylene glycol dimethyl ether with spray-dried potassium fluoride converts 4-chlorobenzaldehyde to 4-fluorobenzaldehyde in 74% yield [67] In addition, the halogen of a primary alkyl chloride or bromide is easily displaced by fluorine in aqueous saturated potassium fluoride and a catalytic amount of hexadecyltributylphosphonium bromide [68] (Table 7 Procedure 4, p 194)... 

Table 7. Reactions of Primary Alkyl Halides with Potassium Fluoride and Hexadecyltributylphosphom um Bromide [6S]...

Condensation of sodium phenoxide witli 2,2,2-trifluoroethyl iodide gives a product of direct substitution in a low yield, several other ethers are formed by eliminatton-addition reactions [7] Use of mesylate as a leaving group and hex amethyl phosphoramide (HMPA) as a solvent increases the yield of the substitution [S] Even chlorine can be replaced when the condensation is performed with potassium fluoride and acetic acid at a high temperature [9] (equations 6-8)... 

Hexafluoropropene and sulfur react at 425 °C in the vapor phase to give hexafluorothioacetone and its dimer [/]. In dimethylformamide, it reacts with potassium fluoride and sulfur to give hexafluorothioacetone dimer, which further reacts with hexafluoropropene to give the E and Z isomers of perfluoro-2,4,6-tris(trifluoromethyl)-5-thia-3-heptene [2] (equation 1). 

MorphoHnosulfur trifluoride and tetrafluoroethylene in the presence of potassium fluoride and 18-crown 6 give morphohnopentalluoroethylsulfur di-fluoride, which is subsequently oxidized sequentially to pentafluoroethanesulfinic acid and pentafluoroethanesulfonic acid [7] (equation 7)... 

Treatment of (1,1 -difluoro-2,5-diphenylsilacyclopentadiene)tricarbonyliron with a mixture of potassium fluoride and 18-crown-6 gives 279 [88J0M(347)C1]. 

Thallium(III), particularly as the trifluoroacetate salt, is also a reactive electrophilic metallating species, and a variety of synthetic schemes based on arylthallium intermediates have been devised.75 Arylthallium compounds are converted to chlorides or bromides by reaction with the appropriate cupric halide.76 Reaction with potassium iodide gives aryl iodides.77 Fluorides are prepared by successive treatment with potassium fluoride and boron trifluoride.78 Procedures for converting arylthallium compounds to nitriles and phenols have also been described.79... 

Use of caesium fluoride as base to effect condensation caused an explosion in absence of solvent. Pyridine or potassium fluoride, and use of dichloromethane gave satisfactory results. 

Diphenylsilane reacts with two equivalents of neat n-heptanal in the presence of anhydrous cesium fluoride within three minutes at room temperature to form di-n-hep toxy diphenylsilane quantitatively (Eq. 162).319 Potassium fluoride and potassium phthalate are considerably less effective promoters, even at temperatures up to 140°.319... 

Goswami and Sarkar3 claimed to have prepared methyl and ethyl fluoroformates by the action of thallium fluoride on the corresponding chloroformates. These fluoroformates were described as powerful lacrimators. We found that no appreciable reaction took place between potassium fluoride and ethyl chloroformate in boiling carbon tetrachloride or nitrobenzene. Ethyl fluoroformate could, however, be readily produced by the action of potassium fluoride on ethyl chloroformate by using the autoclave technique. It was found not to have the lacrimatory properties claimed for it, and was non-toxic in comparison with M.F.A. This non-toxicity was to be expected, as the fluoroformate contains the COF and not the CH2F- group. 

Fluoroacetamide has also been prepared by heating a mixture of potassium fluoride and chloroacetamide at 135° under reduced pressure when fluoroacetamide and unchanged chloroacetamide distil over.3 The reaction can also be carried out in xylene solution at ordinary pressure,4 but the yield is only 55 per cent. However, the method has been improved lately, although the product still contains unchanged chloroacetamide. ... 

Addition of nitroalkanes 402 (R = Me, Bu, Ph etc.) to methyl acrylate without a solvent in the presence of Amberlyst-21 gives good yields of the esters 403436. An analogous reaction with electrophilic acetylenes, e.g. dimethyl acetylenedicarboxylate, in the presence of potassium fluoride and tetrabutylammonium chloride yields adducts 404 as mixtures of geometrical isomers437. 

The two-fold Michael addition of nitroethane to methyl propiolate in the presence of potassium fluoride and the phase-transfer catalyst tetrabutylammonium chloride leads to the diester 432. Treatment of nitroethane with methyl propiolate under these conditions, followed by methyl vinyl ketone, leads to the mixed adduct 433460. 

Sir Humphry Davy attempted to isolate this unidentified element through electrolysis—but failed. It was not until 1824 that Jons Jakob Berzehus (1779—1848), who had earlier discovered cerium, osmium, and iridium, became the first person to separate the element silicon from its compound molecule and then identify it as a new element. Berzehus did this by a two-step process that basically involved heating potassium metal chips with a form of silica (SiF = silicon tetrafluoride) and then separating the resulting mixture of potassium fluoride and silica (SiF + 4K —> 4KF + Si). Today, commercial production of sihcon features a chemical reaction (reduction) between sand (SiO ) and carbon at temperatures over 2,200°C (SiO + 2C + heat— 2CO + Si). 

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 same authors (77) also investigated the Michael addition of nitromethane to a,/l-unsaturated carbonyl compounds such as methyl crotonate, 3-buten-2-one, 2-cyclohexen-l-one, and crotonaldehyde in the presence of various solid base catalysts (alumina-supported potassium fluoride and hydroxide, alkaline earth metal oxides, and lanthanum oxide). The reactions were carried out at 273 or 323 K the results show that SrO, BaO, and La203 exhibited practically no activity for any Michael additions, whereas MgO and CaO exhibited no activity for the reaction of methyl crotonate and 3-buten-2-one, but low activities for 2-cyclohexen-l-one and crotonaldehyde. The most active catalysts were KF/alumina and KOH/alumina for all of the Michael additions tested. 

Another electrolysis process involves electrodeposition of dense, high-puri-ty tantalum metal. In this electrolysis, electrolyte consists of potassium fluotantalate and potassium fluoride and the anode is made of tantalum upon which electrodeposition from the fused salt occurs. 

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. 

Fluorophosphites are prepared by a two step sequence. The initial step is the reaction of phenolic materials with phosphorus trichloride to prepare a chlorophosphite intermediate. The chlorophosphite is then treated with a fluoride source to convert the chloro- intermediate into the desired fluorophosphite product. Many different fluoride sources have been described in the literature including anhydrous hydrogen fluoride, anhydrous potassium fluoride, and antimony trifluoride. While any of these fluoride sources can be used successfully, we have found that antimony trifluoride (10) works well for small scale, lab preparations. 

A recent study (57) indicates the disulfide can also be formed by reaction of hexafluoropropylene with potassium fluoride and sulfur. It appears that the key intermediate in this reaction is the anion (CF3)2CFSe. 2,2,4,4-Tetrakis(tri-fiuoromethyi)-l,3-dithietane and (CF3)2CFSCF=C(CF3XCF2)2CF3 are also said to be formed. 

Draw the electron dot structure of potassium fluoride and show how the electron is transferred between the elements potassium and fluorine to create the ionic compound. 

The trialkyl(trifluoromethyl)tin can also be prepared via the reaction of triphenylphosphine and dibromodifluoromethane followed by the treatment with potassium fluoride and trialkyltin chloride [104,105] (Scheme 37). 

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