Fluorination with alkaline fluorides

Because of the high lattice energy of inorganic fluorides, substitutive fluorination with alkaline fluorides in aprotic solvents is always a two-phase reaction which is very dependent on the origin and the preparation of the solid reagent. 

Replacement of fluorine occurs when l,l,l-trifluoro-2,2-dihaloethanes 1 are treated with alkaline alkoxides.59 The products, alkyl 1,1 -difluoro-2,2-dihaloethyl ethers, are probably formed by two separate reactions these are elimination of hydrogen fluoride to give an alkene, followed by addition of the alcohol.59... 

Chemical nature and concentrations of the constituants In a first step, the physical parameters were kept constant (180°C, 24 h, autogenous pressure). Different studies proved first that if NH4F is used instead of HF as a source of F, only one structure type, called CJ2 or NH4A1P04(OH)o.3Fo.7, appears whatever the nature of the amine in the system. Attempts with other alkaline fluorides provide open framworks without incorporated fluorine [29], This explains that HF was used in the following. 

Analysis of the oxyfluoride for osmium and fluorine followed alkaline hydrol3rsis in a closed vessel. A sealed longnecked capsule, containing the sample, was broken by turning a stopcock, into the hore of which, the neck of the capsule extended. The capsule was wholly immersed in aqueous alkali. Osmium was determined by reduction to the metal with hydrazine hydrate.Fluorine was estimated by the Willard and Winter distillation followed hy precipitation of fluoride as PbClF. Fluorine was also determined in the filtrate following the osmium precipitation (Found F, 31T Os, 61-9, F,OOs requires F, 31-5 O, 5-4 Os, 63-1%). 

Terminally fluorinated carbohydrates may be obtained by treating the tosyl esters, or the more reactive mesyl esters, with potassium fluoride in methanol. Because of the alkaline reaction of potassium fluoride, the remaining hydroxyl groups must be protected, as for example, by acetal formation,... 

There are many unique and otherwise difficult reactions that are induced essentially by the strong interaction between fluorine and a special atom. Because of its hardness, fluorine interacts strongly with alkaline and alkaline earth metal ions, and in particular with neutral group III elements. Table 3.1 lists the strengths of chemical bonds between fluorine and other atoms, as a measure for the interaction between fluorine and other atoms [1], The theoretically calculated fluoride affinity also serves as a measure of interaction between a fluoride ion and an inorganic Lewis acid [2]. 

ANILINE (62-53-3) Combustible liquid (flash point 158°F/70°C). Unless inhibited (usually by methanol), readily able to polymerize. Violent reaction, including the possibility of fire, explosion, and the formation of heat- or shock-sensitive compounds may result from contact with acetic anhydride, benzene diazonium-2-carboxylate, aldehydes, alkalis, benzenamine hydrochloride, boron trichloride, l-bromo-2,5-pyrrolidinedione, chlorosulfonic acid, dibenzoyl peroxide, fluorine nitrate, halogens, hydrogen peroxide, isocyanates, oleum, oxidizers, organic anhydrides, ozone, perchloryl fluoride, perchromates, potassium peroxide, P-propiolactone, sodium peroxide, strong acids, trichloromelamine. Strong reaction with toluene diisocyanate. Reacts with alkaline earth and alkali metals. Attacks some plastics, rubber, and coatings. Incompatible with copper and copper alloys. 

Perfluoroalkanesulfonic acids are mainly prepared by two methods. The first method based on electrochemical fluorination (ECF) in anhydrous hydrogen fluoride (AHF) is the most practical. Although fluorination of the alkanesulfonic acids cannot be carried out directly by ECF9,10, the alkanesulfonyl fluorides can be successfully fluorinated with fairly high yields. The prefluorinated sulfonyl fluoride produced may then be converted to the corresponding salt by alkaline hydrolysis. The free acids were obtained either by their distillation from a solution of the alkaline metal sulfonate in concentrated sulfuric acid or by treatment of the salt with strong acid-type ion exchange resin (equation 1). 

In general, two methods are used to determine trace amounts of fluorine in different natural materials, fodder, and foodstuffs. These are photometric determination based on the reaction of fluoride ions with the lanthanum-alizarin complexing agent and electrochemical measurements of fluoride concentrations by means of F-selective electrodes (Brill 1995). When measuring fluorine in the fluids and tissues of mammals, it is pre-separated by distillation or diffusion. As applied to fluorine determination in plants, good results are demonstrated using alkaline hydrolysis with subsequent fluoride concentration measurements, or in an acid medium by means of ion-selective potentiometry (Galloway et al. 1975). 

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). 

For many years fluorine has been deterrnined by the Willard-Winters method in which finely ground ore, after removal of organic matter, is distilled with 72% perchloric acid in glass apparatus. The distillate, a dilute solution of fluorosiUcic acid, is made alkaline to release fluoride ion, adjusted with monochloroacetic acid at pH 3.4, and titrated with thorium nitrate, using sodium a1i2arine sulfonate as indicator. 

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