Anhydrous Hydrogen Fluoride, AHF

The greatest use of AHF is in the production of fluorinated carbon compounds, the so-called HCFCs and HFCs. These materials are essential cooling agents, foam blowing agents, fire-fighting agents, solvents and raw materials for the production of fluorinated monomers for the plastics industry. 

Additional major uses of AHF in organic chemistry are for Balz-Schiemann reactions [2], alkylation reactions in the petrochemical industry [1], reactions with SF4 in AHF to generate CF3- or CF2H-groups [3] and electro fluorination reactions [4]. 

Since the production of elemental fluorine is only possible by anodic oxidation of fluoride ions, the electrolysis of HF mixed with KF as an electrolyte is the most important electrochemical application of AHF [5]. See below for additional information regarding the application of fluorine and its downstream product sulfur hexafluoride, SFg. 

The separation of uranium isotopes by the nuclear industry also needs anhydrous hydrogen fluoride in the first step to transform uranium oxide into UF4. For the further oxidation of UF4 to the gaseous UFs, which is centrifuged into isotopic pure fractions in a following step, elemental fluorine is needed. 

---

Oxonium compounds are well known, especially in the field of super acids where traces of water are immediately converted to compounds like H3OAsF6 [132], The formation of such salts is most easily understood as H20 replacing the weaker base HF from H2F+ cations present in solutions of strong Lewis acids in anhydrous hydrogen fluoride (aHF). 

Anhydrous hydrogen fluoride (aHF) is a medium to good solvent for many fluorides in particular for those with polymeric structures. The solubility of ternary fluorides, especially those of transition metals, depends strongly on the counterion, for... 

On the basis of self-ionic dissociation, these compounds can be prepared by acid-base reactions. Heteropolyhalogen cations are usually prepared by reacting the parent compound with a Lewis acid (equation 51) in which XY = interhalogen and MYm = Lewis acid, for example, hahdes of B, Al, P, As, and Sb, and so on (equations 52 and 53). Such reactions can be performed by direct interaction of the reactants with an excess of the more volatile reactant, which can then be pumped off, after completion of the reaction, leaving behind the pure product. Sometimes it is preferable to perform such reactions in solution, such as in anhydrous hydrogen fluoride (AHF), and pump off the solvent at the end of the reaction. 

Abstract F acceptors (BFs, AsFs, SbFs, or BiFs) added to solutions of NiFs " salts in anhydrous hydrogen fluoride (aHF) below -65 °C precipitate the tan solid NiFa. This solid, preserved at <-65 °C, is quantitatively converted, by 2 equiv of F donor (XeFs or KF) in aHF, to dissolved NiFe ". Dry NiF4 loses Fa above -60 °C, the decomposition to nearly black NiFj becoming rapid at 0 °C. When the dry NiF4 is prepared from KaNiFe, inclusion of some K leads, on thermolysis at 0 °C, to a pyiochlore form of NiFs (P-NiFs). P-NiFs contains K+ in the open channels, with K NiFs, a R5 0.1, The nearly cubic P-NlFs unit cell is rhombohedral oo — 9.933(3) A, a = 91.01(3)°, 980 h ,... 

When metallic gold is exposed to elemental fluorine (F2) at room temperature in the presence of the ionizing solvent liquid anhydrous hydrogen fluoride (aHF) containing an alkali fluoride, the metal is quickly dissolved to give the alkali salt of the anion... 

In liquid anhydrous hydrogen fluoride (AHF), together with the strong fluoride ion acceptor AsFj, the Agp3 reacted to form a blue solution with elimination of Fj. From this solution the previously described Ag(ll) salt, AgFAsFj, was isolated, the overall reaction being... 

Abstract Gold at 20 °C with F in anhydrous hydrogen fluoride (aHF) acidified with SbFs dissolves to a red solution from which orange Au lStaFs) crystallizes on removal of volatiles. Au(Sbp6)2 is trichnic with a — 5.300(1)... 

Clifford et al. [1] and Clifford and Morris [2] were pioneers in defining the anhydrous hydrogen fluoride (aHF) solvent system on which much of the work in these laboratories, including this paper, is based. 

NiFz was oxidized at 20°C, to by sunlight- or ultraviolet light-irradiated Fj in liquid anhydrous hydrogen fluoride (aHF)... 

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). 

Alkanes can be fluorinated by means of electrolysis in hydrogen fluoride. This important reaction is reviewed in Reference. Electrochemical fluorination in anhydrous hydrogen fluoride (AHF), the so-called Simons process, involves the electrolysis of organic compounds (aliphatic hydrocarbons, halohydrocarbons, acid halides, esters, ethers, amines) at nickel electrodes. It mostly leads to perfluorinated compounds. It is, however, considerably accompanied by cleavage and rearrangement reactions. As mechanism, the formation of carbocations by an ECE mechanism is assumed through oxidation of the hydrocarbon by higher-valent nickel fluorides. 

If the uranium is to be used as a metal or as feed material for isotope enrichment plants, the uranium dioxide is treated with anhydrous hydrogen fluoride (AHF) to form UF4 (Figure 1.11). The UF4 can then be reduced metallothermically with magnesium or calcium to produce metallic uranium (still of natural isotope composition), which can also be used to fuel some types of reactors. However, if enrichment of the U isotope is planned, the UF4 is fluorinated to produce UFg, which is the feed material for most commercial enrichment plants. The uranium hexafluoride is then transferred into 10-14 ton cylinders where it solidifies. These cylinders with the solid UFg are stored until ready to be shipped to the enrichment plant. 

Functionalized Inorganic Fluorides 7.2.1 Anhydrous Hydrogen Fluoride, AHF... 

---