Reduction fluoride

The use of this direct oxide reduction process is replacing fluoride reduction as it eliminates neutron exposure to operating personnel (alpha particles from plutonium decay have sufficient energy to eject neutrons from fluorine by the a,n reaction) and eliminates reduction residues which require subsequent recovery. 

Christensen, D. C. Rayburn, J. A. "Pyrochemical Recovery of Plutonium Fluoride Reduction Slag," Los Alamos National Laboratory, In Press. 

Fluorides are nonhygroscopic, and their melting points are higher than those of the corresponding chlorides. Besides, the fluoride reduction reactions are considerably more exothermic. The prime examples of the use of fluorides as intermediates are the reduction of uranium tetrafluoride by calcium or magnesium the reduction of rare earth fluorides by calcium, reduction of beryllium fluoride by magnesium and the reduction of potassium tantalum double fluoride by sodium. 

Figure 4.24 Reactor for uranium fluoride reduction with calcium.

Neither calcium nor magnesium is used as the reducing agent in the production of tantalum by fluoride reduction. The intermediate used is potassium tantalum fluoride (K2TaF7), and the reducing agent is sodium. The choice of sodium is primarily guided by the need to produce tantalum in the powder form. The pertinent reaction is ... 

Treatment of intermediate 31 with 2.2 equiv of 4-FB A in EtOH at 72 °C afforded 35 as a white crystalline solid in 90% isolated yield (Scheme 6.9). Hydrogenation in the presence of 5% of Pd/C and 1 equiv of MsOH, efficiently removed the Cbz-protected group. MsOH was used to prevent fluoride reduction resulting in low levels of the des-fluoro by-product. Catalyst filtration, followed by neutralization of the crude reaction mixture with NaOH, afforded free amine 36 as a white crystalline product in 99% isolated yield. Free-amine 36 was isolated as a dihydrate which necessitated drying prior to coupling with oxadiazole chloride 2. 

The fluoride reduction technique is being replaced in production plants by the metallothermic reduction of an oxide (24). Direct oxide... 

Zinc amalgam, or electrochemical reduction of porphyrinatoniobium(V) oxide acetates led to [NbIVOL] (L = OEP, TPP, TPTP).566 The [NbOLF]- anions have been obtained by controlled potential electrolysis of (i) the corresponding Nbv oxo acetate in the presence of PFg and (ii) the appropriate Mr oxo fluoride. Reduction by zinc amalgam of [M)LX3] (X = Q, Br) gave [NbtvLX2] 327 the ESR spectra of the six-coordinate complexes in frozen THF solution are consistent with trans coordination. 

Knighton, J. B. Auge, R. G. Berry, J. W. Molten Salt Extraction of Americium from Molten Plutonium Metal, Rockwell International Rocky Flats Plant, RFP-2365, March 12, 1976. Mullins, L. J. Morgan, A. N. A Review of Operating Experience at the Los Alamos Plutonium Electrorefining Facility, 1963-1977, Los Alamos National Laboratory, LA 9843, Dec. 1981. Christensen, D. C. Rayburn, J. A. Pyrochemical Recovery of Plutonium Fluoride Reduction Slag, Los Alamos National Laboratory, In Press. 

Dependence of Potential and Selectivity of Piny I Fluoride Reduction in 2 N HCIO on Heat of Sublimation" ... 

Figure 25 shows such plots for vinyl chloride and fluoride reduction on... 

The apparatus used for the production of metal on the few microgram scale via fluoride reduction has been improved considerably between its use for the first preparation of Bk metal (2) and the more recent preparations of Bk metal on the half-milligram scale (13,14) and Cf metal on the 10 yg scale (8) ... 

The best described case is the one of potassium tantalum fluoride reduction. This salt is currently obtained in the Marignac separation, from the potassium columbium oxyfluoride, by crystallization. The fully dried salt is mixed with clean sodium chips, pressed lightly in a steel bomb which is sealed and heated externally with gas. After the flash the cooled bomb is drilled out and the cake is treated with alcohol, water, and various acids. The powder obtained is processed to compact metal by pressing in bars and high vacuum sintering. 

THP-Protected lactamide 459 has been used to synthesize (2R, 3 S)-2,3-(cyclohex-ylidenedioxy)butanal (462), a key intermediate for the synthesis of L-daunosamine, the amino sugar component of natural anthracycline antibiotics [85] (Scheme 66). The crucial reaction in the sequence is the yw-selective hydrosilane/fluoride reduction of ketone 460, which... 

Scheme 23 Aryl-fluoride reductive elimination from an isolated Pd(IV) fluoro complex...

Fluoride Reduction of tooth decay Excessive amounts are harmful for the teeth of children... 

There are many other reactions of relevance to the preparation of fluorides. Some occur at high pressures. Some involve decomposition reactions (of hydrates or fluorides). Reduction reactions with metals, with CO, PF3 and other reagents as well as with thermal treattnent are used to prepare fluorides of metals in lower oxidation states (EuFj EuF, MoF M0F3, etc.). 

Isobe started with hexyl-functionalized dibromo crysene 76, and accessed the metallocycle 78 via the diboronate 77 using platinum chloride and cesium fluoride. Reductive elimination with triphenylphosphine offered the hydrocarbon 79 cleanly. 

Yandulov DV, Tran NT (2007) Aryl-Fluoride reductive elimination from Pd(II) Feasibility assessment from theory and experiment. J Am Chem Soc 129 1342-1358... 

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