Hydrogen fluoride basicity

Thus nitric acid behaves as a base in hydrogen fluoride. Hence increases of conductivity when substances dissolve in hydrogen fluoride may be due to acidic or basic behaviour. 

The relative basicities of aromatic hydrocarbons, as represented by the equilibrium constants for their protonation in mixtures of hydrogen fluoride and boron trifluoride, have been measured. The effects of substituents upon these basicities resemble their effects upon the rates of electrophilic substitutions a linear relationship exists between the logarithms of the relative basicities and the logarithms of the relative rate constants for various substitutions, such as chlorination and... 

Fused basic salts and basic oxides react with vitreous siUca at elevated temperatures. Reaction with alkaline-earth oxides takes place at approximately 900°C. Hahdes tend to dissolve vitreous siUca at high temperatures fluorides are the most reactive (95). Dry halogen gases do not react with vitreous siUca below 300°C. Hydrogen fluoride, however, readily attacks vitreous siUca. 

Silver Fluoride. Silver fluoride, AgF, is prepared by treating a basic silver salt such as silver oxide or silver carbonate, with hydrogen fluoride. Silver fluoride can exist as the anhydrous salt, a dihydrate [72214-21-2] (<42° C), and a tetrahydrate [22424-42-6] (<18° C). The anhydrous salt is colorless, but the dihydrate and tetrahydrate are yellow. Ultraviolet light or electrolysis decomposes silver fluoride to silver subfluoride [1302-01 -8] Ag2p, and fluorine. 

The total yield of products from alkanecarboxyhc acids increases, in most cases, by addition of anhydrous hydrogen fluoride. The optimum hydrogen fluoride concentration is much higher than catalytic and is related to the basicity of a carbonyl group. A mechanism for the formation of both 1,1,1-trifluoroalkanes and bis(l,l-difluoroalkyl) ethers has been proposed [206] (equation 102)... 

The more basic of the polynuclear benzenoid hydrocarbons dissolve in concentrated sulfuric acid, probably with the formation of simple carbonium ions.263 Benzene itself is only slightly soluble, but exchanges hydrogen with DaS04.866 Benzene and toluene will dissolve in a mixture of hydrogen fluoride and boron trifluoride.867 268 Pyrene in hydrogen... 

The noteworthy advantages of the allyl ester are (a) it is readily introduced into amino acids (b) after isomerization (to 1-propenyl) by a palladium(O) catalyst it may be removed under weakly acidic or basic and neural conditions (32), even if sulfur-containing amino acids are present (34) (c) it shows orthogonal stability to the tert-butyloxycarbonyl and 9-fluorenylmethoxy-carbonyl groups (10) and (d) it is not affected by the hydrogen fluoride-pyridine complex (35). 

A basic step in hydrofluoric acid manufacture is the reaction of sulfuric acid with fluorspar (calcium fluoride) to produce hydrogen fluoride and calcium sulfate. Spent alumina is also generated by the defluorination of some hydrofluoric acid alkylation products over alumina. It is disposed of or sent to the alumina supplier for recovery. Other solid residuals from hydrofluoric acid alkylation include any porous materials that may have come in contact with the hydrofluoric acid. 

Reaction with water is slow, forming a hydrate. The product decomposes slowly at ambient temperature with liberating hydrogen fluoride, leaving a basic fluoride, CuFOH. The dihydrate hydrolyzes to oxyfluoride Cu(OF)2 in hot water. 

Compounds which tend to eliminate hydrogen fluoride in the presence of a base are 1.2-difluoroalkancs, oqa -difluoro ethers, a,a -difluoro sulfides, /1-fluorocarbony] compounds, 1,1-diaryl- and 1,2-diarylpolyfluoroalkanes, 277-acyl fluorides and polyfluoroalkylammonium salts. Polyfluoroalkancs (see Table 2) are relatively labile towards basic reagents. If two elimination pathways are possible, such as in 1,1,2.3,3,3-hexafluoropropanc (1), hydrogen is eliminated from the carbon bearing fewer fluorines.11,2... 

The elimination of two or three molecules of hydrogen fluoride requires prolonged reaction time and higher base concentrations or sometimes molten potassium hydroxide. The yields are generally low. The alternative utilization of basic ion-exchange resins results in milder reaction conditions (50-60 C) and higher yields.94... 

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