Hydro fluorination

Starting from rare earth oxides, rare earth fluorides can be prepared by the hydro-fluorination of the oxides with anhydrous hydrogen fluoride. For example,... 

The actual fluoride-forming reaction in the ammonium bifluoride route is hydro-fluorination. Hydrogen fluoride, which is present in chemical combination in the bifluoride, is readily released on heating. Bifluorides are easier to handle than hydrogen fluoride. The particular advantage of ammonium bifluoride over other alkali hydrogen fluorides is that it is volatile, and thus can be readily distilled out from the reaction mixture. 

Bruns and Haufe have described the first examples of a transition metal complex mediated asymmetric ring opening (ARO) of both meso- and racemic epoxides via formal hydro-fluorination [23]. Initial attempts with chiral Euln complexes led to very low asymmetric induction. Opening of cyclohexene oxide 30 with potassium hydrogendifluoride in the presence of 18-crown-6 and a stoichiometric amount of Jacobsens chiral chromium salen complex 29 [24a] finally yielded two products 31 and 32 in a 89 11 ratio and 92% combined yield, the desired product 31 being formed with 55% ee. Limiting 29 to a catalytic amount of 10 mol% led to an increase in the ratio of 31, however, with the enantiomeric excess dropping to 11% (Scheme 5). 

The first step in the two-step synthesis of l,l-difluoro-1-phcnylethane (4) is the hydro-fluorination of phenylacetylene with hydrogen fluoride cither in diethyl ether at 0 C (18% yield) or at 150 C in the gas phase with 13-14% mercury(II) oxide on activated carbon as catalyst to give the vinyl monomer... 

Protactinium pentafluoride, which is isostructural with -UFg (Table III). is best prepared (160) by fluorination of the tetrafluoride at 700°C (Fig. 1). It has been obtained in an amorphous state (38) by hydro-fluorination of the pentachloride at 200°C and, contaminated with... 

The commercial method begins with hydrofluorina-tion of acetylene followed by chlorination,by hydrofluorination of trichloroethane, or by hydro-fluorination of vinylidene chloride. In each case, the final product, l-chloro-l,l-difluoroethane, is stripped of a molecule of hydrochloric acid to yield vinylidene fluoride. 

Both plutonium trifluoride and tetrafluoride can be prepared by hydro-fluorination of plutonium dioxide. The oxidation-reduction relations of plutonium (III) and (IV) are such that it is readily possible to specify which of the fluorides shall be the product. If the reaction is carried out under reducing conditions, then the product is PuF3, and under oxidizing conditions, PuF4 ... 

In principle, the fluoride volatility process has fewer stages and is simpler than the conventional process. It consists of reduction of the UOC (yellow cake) to UO2 with hydrogen (derived from cracking anunonia) followed by hydro-fluorination to produce UF4 (green salt) and then fluorination to produce UF (hex). In principle, uranium ore concentrates may be directly fluorinated to produce UFg, but this process consumes large amounts of fluorine and is not applied commercially. 

Conversion to thorium tetrafluoride. This conversion is performed at 566 C by a hydro-fluorination exothermic reaction achieved in a series of screw-fed horizontal reactors made of AlSl 309Nb stainless steel with a screw of lllium R or Inconel in which solid and gases flow countercurrently. During the exothermic reaction the conversion of the thorium dioxide into thorium tetrafluoride occurs with the recovery of hydrofluoric acid as a commercial byproduct according to the following scheme ... 

The commercial method begins with hydro-fluorination of acetylene followed by chlorination,[ i... 

Low temperature fluorination techniques (—78° C) are promising for the preparation of complex fluorinated molecules, especiaUy where functional groups are present (30), eg, fluorination of hexamethjiethane to perfluorohexamethylethane [39902-62-0] of norbomane to perfluoro- (CyF 2) 1-hydro undecafluoronorbomane [4934-61 -6] C HF, and of adamantane to 1-hydropentadecafluoroadamantane [54767-15-6]. 

Fluorination of tetrachlorophthalic acid hemihydrate with an excess of sulfur tetrafluoride, or of tetrachlorophthalic anhydride with a sulfur tetrafluonde-hydro-gen fluoride reagent, provides an efficient synthesis of 4,5,6,7- tetrachloro-1,1,3,3-tetrafluorol,3-dihydroisobenzofuran. 3,4,5,6-Tetrachloro-2-(trifluoromethyl)-benzoyl fluoride is formed as a by-product [217] (equation 111). 

The ionization energy of the hydrogen atom, 313.6 kcal/mole, is quite close to that of fluorine, so a covalent bond between these two atoms in HF is expected. Actually the properties of HF show that the molecule has a significant electric dipole, indicating ionic character in the bond. The same is true in the O—H bonds of water and, to a lesser extent, in the N—H bonds of ammonia. The ionic character of bonds to hydro-... 

Perfluoroalkyl)ethane thiols have been used as precursors to fluorinated surfactants and products for hydro- and oligophobic finishing of substrates such as textiles and leather (1). The synthesis of 2-(perfluoroalkyl)ethane thiol and a byproduct bis-(-2-perfluoroalkylethane)-disulfide (5-10%) has been practiced via the reaction of 2-(perfluoroalkyl)ethane iodide with thiourea to form an isothiuronium salt which is cleaved with alkali or high molecular weight amine as shown in Equation 1 for 2-(perfluorohexyl)ethane iodide (1). 

PFCs are a large group of chemicals characterized by a fully fluorinated hydro-phobic chain and an hydrophilic head. These compounds are often used as coating... 

In recent times, the development of new ionic liquids has made great progress. Important developments include a range of new halogen-free ionic liquids (e.g., benzenesulfonates [13], toluenesulfonates, alkylsulfates [14], hydro-gensulfate [15, 16], dicyanamides [17], thiocyanates [18], etc.), as well as functionalized (task-specific) [19-23], fluorinated [24], deuterated [25] and chiral ionic liquids [26-30]. 

Several direct aromatic fluorinations are carried out with the positron-emitting isotope 18F which is an essential component in the operation of Positron Emitting Tomography (PET). Tyrosine is dissolved in hydrogen fluoride and when fluorinated with 18F-F it produces mainly 3-[ 8F]fluorotyrosine (8) without losing its optical activity. The use of nonacidic solvents reduces the yields considerably.52 3,4-Dihydroxyphenylalanine is similarly fluorinated either in hydro-... 

Scheme 4.25 provides fluorine NMR data for some 3,3-difluoro-2-hydro-xycarboxylic acids, while Scheme 4.26 gives proton and fluorine data for examples of RCH(OH)CF2XPh, where X = S, Se, and Te. 

However, we also knew that the smaller fluorine atoms would still permit of a high rate of hydro -... 

Likewise, unsymmetrical fluorine containing carbodiimides are obtained from a-hydro-perfluoroisopropyl isocyanate. ... 

The hydroxy group in a-hydroxy ketones and a-hydroxy esters can be replaced by fluorine using sulfur tetrafluoride. fo obtain good yields of the fluoro esters or fluoro ketones, the reaction conditions must be carefully controlled. In the case of a-hydro.xy ketones 1. diethyl ether is the solvent of choice for the reaction. Without a solvent, fluorination of the carbonyl group atid other side reactions cannot be avoided. ... 

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