Fluoride mixtures, production purification

Since commercial fluorides that have a low concentration of the usual nuclear poisons arc available, the production of fluoride mixtures is largely a purification process designed to minimize corrosion and to ensure the removal of oxides, oxyfluoridos, and sulfur, rather than to improve the neutron economy. The fluorides are purified by high-temperature treatment with anhydrous HF and H2 ga.ses, and are subsequently stored in sealed nickel containers under an atmosphere of helium. 

Some examples for the isolation of the desired poly(trifluoromethyl) compounds from product mixtures by chemical purification have been reported. In the reaction of benzene-1,2.3-tricarboxylic acid with sulfur tetrafluoride/hydrogen fluoride a mixture of 1.2,3-tris(tri-fluoromethyl)benzene (9). 1,1,3,3-tetrafluoro-4-(trifluoromethyl)-l,3-dihydroisobenzofuran... 

Reduction of the lactone 137 to the corresponding lactol 138 necessitated use of DIBAL quenching the reaction with methanol followed by workup with aqueous potassium sodium tartarate furnished the product as a clear viscous oil that solidified on standing to a white solid. The anomeric hydroxyl group was conveniently protected by the formation of terf-butyldimethylsilyl ether by treatment with rert-butyldimeth-ylsilyl chloride, imidazole, and A,A-dimethylaminopyridine. Further activation of the anomeric position in compound 139 with trimethylsilyl bronfide followed by treatment with l-t-butyldimethysiloxy-3-butyne and n-butyUithium yielded a transicis mixture (1 1) (140) that was used without further purification. Reaction of compound 140 with tetrabutylammonium fluoride led to deprotection of the hydroxy functionality. The resulting transicis mixture of the alkynols was subjected to extensive chromatography and repeated crystallization to obtain a tran -alcohol (141) as a white crystalline solid. Further elaboration to 131 was carried out by appropriate modifications of a literature procedure. ... 

A solution of the 2,6-dioxa-l,8-diaminooctane 85 (74 mg, 0.5 mmol) and paraformaldehyde 86 (1.0 mmol) in MeOH (200 mL) was stirred at room temperature for 2 h. Two solutions, one of diacid 84 (392 mg, 0.5 mmol) and another of cyclohexylisocyanide 25 (90 pL, 1.0 mmol) in 20 mL of MeOH each, were simultaneously, slowly added to the reaction mixture using syringe pumps (flow rate 0.5 mL h ). After addition was completed, the reaction mixture was stirred for 8 h and concentrated under reduced pressure to dryness. The resulting crude product was dissolved in 50 mL of THF and tetra- -butylammonium fluoride trihydrate (535 mg, 1.5 mmol) was added. The reaction mixture was stirred at room temperature for 12 h and then diluted with 150 mL of EtOAc. The solution was washed with aqueous 10% NaHCOs (2 x 30 mL) and brine (50 mL), dried over anhydrous Na2S04 and evaporated under reduced pressure to dryness. Flash column chromatography purification (CH2Cl2/MeOH 20 1) yielded the macrocycle 87 (224 mg, 54%) as a pale yellow oil. 

A dry technique for production and purification of metal fluorides, their mixtures, and fusion cakes without gaseous HF was also used in material studies for conversion of UO2 and Th02 to anhydrous tetrafluorides and for the removal of impurity oxide compounds from major solvent constituents [1]. Heating of these mixtures is accompanied by successive reactions of synthesis and decomposition. The total chemical reaction can be described by the equation ... 

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