Fluorination 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). 

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

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 ... 

Diazoalkanes, diazoketones, and diazoacetates can be fluorinated at 0 C with the loss of nitrogen by treatment with 70 % hydrogen fluoride/pyridine (a,a-hydrofluorinations) in 30-95 % yield.31 133 Furthermore, diazo ketones and diazoacetates when N-halosuccinimide is additionally introduced into the hydrogen fluoride medium.133... 

The HF-SbF5 superacid finds numerous additional useful applications in other fluorination reactions. Ally lie amines are hydrofluorinated in HF-SbF5 (7 1) to give /3-fluoro-substituted products (—20°C, 24—85% yields).545 HF-SbF5 in combination with /V-bromosuccinimide transforms allylic amines and haloalkyl amines into gem-difluoro derivatives (0°C or 20°C, 43-70% yield).546... 

Stable dialkyl ether poly(hydrogen fluoride) complexes have been shown to be convenient and effective fluorinating agents.553 Various open-chain and cyclic alkenes undergo hydrofluorination with dimethyl ether-5 HF (DMEPHF) atroom temperature to furnish the corresponding fluoro derivatives in high yields (73-94%) with excellent selectivities. The fluorination of secondary and tertiary alcohols exhibit similar features. Bromofluorination of alkenes can also carried out with DMEPHF in combination with /V-bromosuccinimide. The homologous diethyl ether and dipropyl ether complexes are also suitable for fluorinations. 

Olah and Li2 have prepared a solid form of this reagent by reaction of anhydrous HF with cross-linked poly-4-vinylpyridine. It is comparable to pyridinium poly (hydrogen fluoride) for hydrofluorination of alkenes and alkynes and fluorination of alcohols, but is easier to handle. Work-up of reactions requires only a simple filtration, and the spent reagent can be regenerated with HF for further use. 

Fluorocarbon products that do not contain chlorine and/or bromine (i.e., fully fluorinated and hydrofluorinated [HFC] products) are not stratospheric ozone-depleters, and production of these products is not being eliminated by the Montreal Protocol. They are, however, restricted by the U.S. Clean Air Act and must be recovered rather than released to the atmosphere. 

In the dry process, introduced by Allied Chemical Corp., the uranium concentrate is pelletized and directly reduced with hydrogen to uranium(IV) oxide at temperatures between 540 and 650°C in a fluidized bed reactor. Hydrofluorination to uranium(IV) fluoride proceeds in two fluidized bed reactors connected in series. After fluorinating the uranium(IV) fluoride formed in a production unit consisting of a flame-reactor and a fluidized bed reactor, the uranium(Vl) fluoride produced is purified in a two stage pressure distillation process. This distillative purification process is necessary, because, in contrast with the wet process, no purification is carried out in earlier stages. 

Uranium trioxide can be converted to UF by a one-step, direct fluorination process, or by the hydrofluorination process which involves three steps (1) reduction of UO to UO 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. 

Toxic mechanism Fluorin derivative substances (indoclon etc.) in contact with the organism release hydrofluorin. Below are described the main damaging mechanisms ... 

In the U.S. Department of Energy (DOE) plant at Paducah and the Comurhex plant at Pierrelatte [B5], UF4 is converted to UF by reaction with fluorine in a tower reactor. Solid UF4 and a slight excess of fluorine gas are fed at the top of a monel tower with walls cooled to around 500°C. Most of the UF4 reacts almost instantaneously with a flame temperature of around 1600°C. Small amounts of unreacted UF4 and uranium oxides are removed from the bottom of the tower and recycled to the hydrofluorination step. 

Subsequently, Boger extended the established methodology to alkene hydrofluorination. Operating in a similar manner, following reductive radieal formation, the intermediate allq l radical species eould be trapped with a radieal fluorine souree ie. Selectfluor ). Similarly, Shen showed that alkenes eould be hydro-trifluoromethylthiolated using a radieal thiotri-fluoromethyl souree with borane as the required hydrogen souree. ... 

Toxicology OSHA PEL/TWA 2.5 mg(F)/m highly toxic corrosive irritant to skin, eyes, and mucous membranes probable poison by inh. causes severe burns TSCA listed Precaution DOT Corrosive reacts violently with water, although incompletely and reversibly hydrolyzed Storage Store under nitrogen refrigerate Uses Catalyst for alkylation, acylation, condensation, polymerization reactions in hydrofluorination of olefins in prod, of substituted pyridines in prod, of petrol, prods. fluorination reagent... 

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