Hydrofluorination

Nickel fluoride is used in marking ink compositions (see Inks), for fluorescent lamps (4) as a catalyst in transhalogenation of fluoroolefins (5), in the manufacture of varistors (6), as a catalyst for hydrofluorination (7), in the synthesis of XeF (8), and in the preparation of high purity elemental fluorine for research (9) and for chemical lasers (qv) (10). 

The commercially preferred monomer precursor HCFC-142b has been prepared by hydrofluorination of acetylene (29), vinyHdene chloride (30—32), or 1,1,1-trichloroethane (33—39). 

Cmde HCl recovered from production of chlorofluorocarbons by hydrofluorination of chlorocarbons contains unique impurities which can be removed by processes described in References 53—62. CICN—CI2 mixtures generated by reaction of hydrogen cyanide and CI2 during the synthesis of (CICN) can be removed from the by-product HCl, by fractional distillation and recycling (see Cyanides) (59). 

In practice, uranium ore concentrates are first purified by solvent extraction with tributyl phosphate in kerosene to give uranyl nitrate hexahydrate. The purified uranyl nitrate is then decomposed thermally to UO (eq. 10), which is reduced with H2 to UO2 (eq. 11), which in turn is converted to UF by high temperature hydrofluorination (eq. 12). The UF is then converted to uranium metal with Mg (eq. 19). 

Halogenation and dehalogenation are catalyzed by substances that exist in more than one valence state and are able to donate and accept halogens freely. Silver and copper hahdes are used for gas-phase reactions, and ferric chloride commonly for hquid phase. Hydrochlorination (the absoration of HCl) is promoted by BiCb or SbCl3 and hydrofluorination by sodium fluoride or chromia catalysts that form fluorides under reaction conditions. Mercuric chloride promotes addition of HCl to acetylene to make vinyl chloride. Oxychlori-nation in the Stauffer process for vinyl chloride from ethylene is catalyzed by CuCL with some KCl to retard its vaporization. 

A polymeric form of the reagent from hydrogen fluoride and poly(4-vinylpyndine) is especially easy to handle [I0 Other tertiary amines can also be employed [II], and a two-phase mixture of hydrogen fluoride-melamine-pentane hydrofluorinates cyclohexene to fluorocyclohexane m 98% yield [12]... 

Depending on the fluonnating agent, diazoalkanes, diazoketones, and diazoesters can undergo hydrofluorination, halofluonnation, and geminal difluonnation reactions... 

Diazoalkanes react with ethyl fluoroformate [S7j and acyl fluorides [87, 55] to give ethyl ot-fluorocarboxylates and ot-fluoroketones, respectively (equation 22) Table 7 lists examples of hydrofluorination [6. 83, 89] and geminal difluori-nation [90] of aryldiazomethanes... 

Fluoromethylketones are obtained by dediazoniative hydrofluorination with anhydrous hydrogen fluoride [91, 92 93] or Olah s reagent [d] (equation 23)... 

By choice of fluorinating agent, either hydrofluorination [6, 98, 99] or halo fluorination [6, 99] of ethyl diazoacetate is realized (equation 26)... 

Los Alamos residue processing yields Pu02 feed that can be easily hydrofluorinated. If the oxide has been prepared by... 

Fluorination and Reduction. Until recently, plutonium dioxide from the calcination of plutonium peroxide was contacted with HF in a rotary hydrofluorinator. The reaction converted Pu02 to PuFt, according to the following equation ... 

Though both hydrofluorination and reduction were accomplished with relative ease, three significant problems were apparent. First, PuFt is a neutron emitter, requiring considerable protective shielding and creating difficulty in handling. Secondly, the use of HF requires costly equipment which must be resistant to corrosion. Finally, the salt from the reduction, CaF2, is not discardable, and must be processed to recover residual plutonium. 

The hydrofluorination of rare earth oxides with ammonium bifluoride is carried out as a batch process by heating the rare earth oxide with 30% excess of high-purity NH4F HF in a platinum boat inside an inconel chamber at 300 °C under a stream of dry air. 

HFC-134a is produced commercially by (1) the hydrofluorination of trichloroethylene via l-chloro-l,l,l-trifluoroethane, (2) isomerization and... 

HCFC-141b is produced commercially by the hydrofluorination of 1,1,1-trichloroethane or 1,1-dichloroethylene (ECETOC 1994). It is manufactured by three companies in the United States. In 1992, total world production was 15,000 tons production was expected to increase to 100,000 tons by 1994 and then be phased out by 2003 (ECETOC 1994). 

Vinyl fluoride may be obtained by the catalytic hydrofluorination of acetylene. 

Ref 2) insol in w dil acids sol in coned acids. Prepd by hydrofluorination of UOa, which, in turn, is obtd from fluid bed reduction of higher oxides by hydrogen. Used for prepn of U metal and UF6 Refs 1) Gmelin-Kraut Syst Number 55(1936),... 

The hydrofluorination of alkenes with anhydrous hydrogen fluoride has been already described extensively in Houben-Weyl, Vol. 5/3, pp 100-101. In the case of ethene, the yield of fluoroethane increases on raising the temperature (90°C, 20-25 atm), however, the procedure should be carried out at lower temperatures with higher alkenes because of their tendency to polymerize thus, 2-fluoropropane is formed in 60-75% yield at 0-45 C. Similar procedures have been described for 2-fluorobutane, 2-fluoro-2-methylpropane and 2-fluoro-2-methyl-butane from but-l-ene, 2-methylpropene and 2-methylbut-2-ene, respectively.63 Cyclohexene reacts at — 78 C with hydrogen fluoride to give fluorocyclohexane (70%) at 100 C polymerization is observed.59,60 Two equivalents of hydrogen fluoride to allene are taken up at — 70 C, to form 2,2-difluoropropane (50%).64... 

Branched alkenes and cycloalkenes react more readily. The hydrofluorinations may be carried out advantageously with 70 % hydrogen fluoride/pyridine (Olah s reagent) using tetrahydro-furan as a solvent,10,31 but a homogeneous system forms in this case. Therefore, the workup procedure was carried out by quenching the reaction mixture with ice water and neutralization with sodium hydrogen carbonate hydrofluorinations of various alkenes in this way are described in ref 40. 

The 5 (or 6)HF Et3N system reacts with a variety of branched alkenes to give tertiary alkyl fluorides. Hydrofluorination of dienes proceeds at the more reactive C = C bond selectively. Thus, ethyl geranate (1) and ethyl nerolate (2) react with 5HF EtaN at the noncon-... 

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