Fluoride potassium

Potassium fluoride (poe-TAS-ee-yum FLU-ride) is a colorless or white crystalline or powdery compound with no odor, but a sharp, salty taste. It has somewhat limited uses in industry and chemical research. 

Potassium fluoride can also be prepared by the direct reaction between hydrofluoric acid and potassium hydroxide H2F2 + 2KOH — 2KF + 2H20. The potassium fluoride thus formed is then dried and crystallized or converted to powder form. 

Potassium fluoride. Silver atom is potassium yellow atom is fluorine, publishers 

Potassium fluoride is used as a fluoridating agent—a substance that provides fluorine atoms to other compounds—in the preparation of organic chemicals. It also finds some use in the field of metallurgy, where it is used as a flux, to finish metals, to make coatings for metals, and in tin 

In France, potassium fluoride is sometimes added to table salt to help prevent dental cavities. 

Freely soluble in boiling water soluble in water and hydrofluoric acid insoluble in alcohol. Aqueous solution erodes glass and porcelain.1 

Breathing dust or swallowing the powder will cause severe poisoning. Irritates the skin, eyes, mucous membranes, and tissue. Prolonged contact can cause shortness of breath, cough, elevated temperature, and cyanosis.2 TLV-STEL-C (as F) 3.0 ppm.3 

Wear a face shield and goggles, laboratory coat, and butyl rubber gloves. Sweep potassium fluoride into a large beaker. In the fume hood, add water (about 13 mL/g of fluoride) and solid calcium hydroxide (about 0.6 g/g of fluoride) to the beaker, and stir for 24 hours. Filter. Wash the filtrate. The solid residue can be discarded with normal 

Reactions for Spillage and Waste Disposal 2KF + Qi(OH)2 - CaP2 + 2KOH calcium fluoride 

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The ability to form hydrogen bonds explains the formation of complex ions such as HFJ and HjFj when a fluoride salt, for example potassium fluoride, is dissolved in aqueous hydrofluoric acid ... 

Alkyl fluorides may be prepared in moderate yield by interaction of an alkyl bromide with anhydrous potassium fluoride in the presence of dry ethylene glycol as a solvent for the inorganic fluoride, for example ... 

In a dry 500 ml. three-necked fiask, equipped with a mercury-sealed stirrer, a 100 ml. dropping funnel and a short fractionating column (1), place a mixture of 116 g. of anhydrous, finely-powered potassium fluoride (2) and 200 g. of dry ethylene glycol (3). Connect the fractionating... 

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. 

Redistil laboratory grade ethylene glycol under reduced pressure and collect the fraction of b.p. 85-90°/7 mm. for use as a solvent for the potassium fluoride. 

Hydrochloric acid should not be used for acidifying the alkaline solution since the yellow colour, due to the ferric chloride formed, causes the Prussian blue to appear greenish. For the same reason, ferric chloride should not be added—as is frequently recommended a sufficient concentration of ferric ions is produced by atmospheric oxidation of the hot alkaline solution. The addition of a little dfiute potassium fluoride solution may be advantageous in assisting the formation of Prussian blue in a readily filterable form. 

It was originally separated from zirconium by repeated recrystallization of the double ammonium or potassium fluorides by von Hevesey and Jantzen. Metallic hafnium was first prepared by van Arkel and deBoer by passing the vapor of the tetraiodide over a heated tungsten filament. Almost all hafnium metal now produced is made by reducing the tetrachloride with magnesium or with sodium (Kroll Process). 

Torgov introduced an important variation of the Michael addition allylic alcohols are used as vinylogous a -synthons and 1,3-dioxo compounds as d -reagents (S.N. Ananchenko, 1962, 1963 H. Smith, 1964 C. Rufer) 1967). Mild reaction conditions have been successful in the addition of ],3-dioxo compounds to vinyl ketones. Potassium fluoride can act as weakly basic, non-nudeophilic catalyst in such Michael additions under essentially non-acidic and non-basic conditions (Y. Kitabara, 1964). 

The metal-ion complexmg properties of crown ethers are clearly evident m their effects on the solubility and reactivity of ionic compounds m nonpolar media Potassium fluoride (KF) is ionic and practically insoluble m benzene alone but dissolves m it when 18 crown 6 is present This happens because of the electron distribution of 18 crown 6 as shown m Figure 16 2a The electrostatic potential surface consists of essentially two regions an electron rich interior associated with the oxygens and a hydrocarbon like exterior associated with the CH2 groups When KF is added to a solution of 18 crown 6 m benzene potassium ion (K ) interacts with the oxygens of the crown ether to form a Lewis acid Lewis base complex As can be seen m the space filling model of this... 

In media such as water and alcohols fluoride ion is strongly solvated by hydro gen bonding and is neither very basic nor very nucleophilic On the other hand the poorly solvated or naked fluoride 10ns that are present when potassium fluoride dis solves m benzene m the presence of a crown ether are better able to express their anionic reactivity Thus alkyl halides react with potassium fluoride m benzene containing 18 crown 6 thereby providing a method for the preparation of otherwise difficultly acces sible alkyl fluorides... 

Chloroacetate esters are usually made by removing water from a mixture of chloroacetic acid and the corresponding alcohol. Reaction of alcohol with chloroacetyl chloride is an anhydrous process which Hberates HCl. Chloroacetic acid will react with olefins in the presence of a catalyst to yield chloroacetate esters. Dichloroacetic and trichloroacetic acid esters are also known. These esters are usehil in synthesis. They are more reactive than the parent acids. Ethyl chloroacetate can be converted to sodium fluoroacetate by reaction with potassium fluoride (see Fluorine compounds, organic). Both methyl and ethyl chloroacetate are used as agricultural and pharmaceutical intermediates, specialty solvents, flavors, and fragrances. Methyl chloroacetate and P ionone undergo a Dar2ens reaction to form an intermediate in the synthesis of Vitamin A. Reaction of methyl chloroacetate with ammonia produces chloroacetamide [79-07-2] C2H ClNO (53). 

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. 

Antimony pentafluoride dissolves ia each to form BrF" 2 bB g 6 which act as acids. Potassium fluoride likewise forms KBrF [15705-87-0] and... 

PbF2 is readily prepared by the action of hydrogen fluoride on lead hydroxide, lead carbonate, or a-lead oxide. It can also be obtained by precipitation from lead nitrate or lead acetate solutions using potassium fluoride, ammonium fluoride, or ammonium bifluoride. 

Properties. Anhydrous potassium fluoride [7789-23-3] is a white hygroscopic salt that forms two hydrates, KF -2H20 [13455-21-5] and KF 4H2O [34341 -58-7]. The tetrahydrate exists at temperatures below 17.7°C. The dihydrate is stable at room temperature and starts to lose water above 40°C. Temperatures on the order of 250—300°C are requited to remove the last few percent of water ia a reasonable period of time. Potassium fluoride does not pyrohydroly2e at temperatures as high as 1000°C (1). Chemical and physical properties of KF are summarized ia Table 1. 

Table 1. Physical and Chemical Properties of Potassium Fluoride...

Potassium fluoride [7789-23-3], KF, is the most frequently used of the alkaU metal fluorides, although reactivity of the alkaU fluorides is in the order CsF > RbF > KF > NaF > LiF (6). The preference for KF is based on cost and availabiUty traded off against relative reactivity. In its anhydrous form it can be used to convert alkyl haUdes and sulfonyl haUdes to the fluorides. The versatility makes it suitable for halogen exchange in various functional organic compounds like alcohols, acids and esters (7). For example, 2,2-difluoroethanol [359-13-7] can be made as shown in equation 9 and methyl difluoroacetate [433-53 ] as in equation 10. 

The preparation of fluoroaromatics by the reaction of KF with perhaloaromatics, primarily hexachloroben2ene, has received considerable attention. Two methods were developed and include either the use of an aprotic, polar solvent, such as /V-methy1pyrro1idinone (8), or no solvent (9). These methods plus findings that various fluoroaryl derivatives are effective fungicides (10) prompted development of a commercial process for the production of polyfluoroben2enes (11). The process uses a mixture of sodium and potassium fluorides or potassium fluoride alone in aprotic, polar solvents such as dimethyl sulfoxide or sulfolane. 

Difluoropyridines. 2,4-Difluoropyridine can be prepared (26% yield) from 2,4-dichloropyridine and potassium fluoride in sulfolane and ethylene glycol initiator (403). The 4-fluorine is preferentially replaced by oxygen nucleophiles to give 2-fluoro-4-hydroxypyridine derivatives for herbicidal apphcations (404). 

Tri-, Tetra-, and Pentafluoropyridines. 2,4,6-Trifluoropyridine can be prepared in 75% yield by catalytic hydrogenolysis (paHadium-on-carbon, 280°C) of 3,5-dichloro-2,4,6-trifluoropyridine [1737-93-5] (416). The latter is synthesized by exchange fluorination of pentachloropyridine with potassium fluoride in polar solvents such as /V-methy1pyrro1idinone (417,418). 3,5-Dichloro-2,4,6-trifluoropyridine is used to... 

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