Silver fluorides solution

Prepared by cathodic reduction of silver fluoride solution ... 

Potassium fluoride (12 g, 0.316 mol) is dissolved in 100 mL of doubly distilled water. Of this solution, 30 mL is combined with 10 mL of the LOOM silver perchlorate stock solution, and potassium perchlorate precipitates. The precipitate is separated by filtration through a small sintered crucible and washed repeatedly with the rest of the KF solution until the total volume equals 100 mL. The same electrolysis cell as for the preparation of Ag20j (part A) is used. The cell is filled with the silver fluoride solution and subsequently cooled to —2° (cf. part A). During electrolysis the current is raised from 10 to 40 mA within 120 min in a linear sweep or in five steps at minimum. Then the current is kept constant at 40 mA for another 120 min. The total charge transferred is 130 mA h thus, 80% of the Ag" cations will have been exchanged by protons. Typical yields are 380 mg per charge. 

Silver difluoride [7783-95-1], AgF2, is a black crystalline powder. It has been classified as a hard fluorinating agent (3) which Hberates iodine from KI solutions and o2one from dilute aqueous acid solutions on heating. It spontaneously oxidizes xenon gas to Xe(II) in anhydrous hydrogen fluoride solutions (20). 

Alkyl fluorides have been prepared by reaction between elementary fluorine and the paraffins, by the addition of hydrogen fluoride to olefins, by the reaction of alkyl halides with mercurous fluoride, with mercuric fluoride, with silver fluoride, or with potassium fluoride under pressure. The procedure used is based on that of Hoffmann involving interaction at atmospheric pressure of anhydrous potassium fluoride with an alkyl halide in the presence of ethylene glycol as a solvent for the inorganic fluoride a small amount of olefin accompanies the alkyl fluoride produced and is readily removed by treatment with bromine-potassium bromide solution. Methods for the preparation of alkyl monofluorides have been reviewed. ... 

O-isopropylidene derivative (57) must exist in pyridine solution in a conformation which favors anhydro-ring formation rather than elimination. Considerable degradation occurred when the 5-iodo derivative (63) was treated with silver fluoride in pyridine (36). The products, which were isolated in small yield, were identified as thymine and l-[2-(5-methylfuryl)]-thymine (65). This same compound (65) was formed in high yield when the 5 -mesylate 64 was treated with potassium tert-hx Xy -ate in dimethyl sulfoxide (16). The formation of 65 from 63 or 64 clearly involves the rearrangement of an intermediate 2, 4 -diene. In a different approach to the problem of introducing terminal unsaturation into pento-furanoid nucleosides, Robins and co-workers (32,37) have employed mild base catalyzed E2 elimination reactions. Thus, treatment of the 5 -tosylate (59) with potassium tert-butylate in tert-butyl alcohol afforded a high yield of the 4 -ene (60) (37). This reaction may proceed via the 2,5 ... 

Acetyl-5-deoxy-l,2-0-isopropylidene-[3-iJ - threo - pent - 4 - enofura-nose (34). (1) From 3-0-acetyl-5-deoxy-5-iodo-1,2-0-isopropylidene- -d-xylofuranose (31). Anhydrous silver fluoride (7.5 grams) was added to a solution of 7.2 grams 26 in dry pyridine (50 ml.), and the mixture shaken at room temperature for 24 hours. The black reaction mixture was diluted with ether (50 ml.), and the supernatant liquid was decanted from the dark, inorganic residue. The residue was further extracted with ether (3 X 50 ml.) and the pyridine-ether solution partially decolorized... 

From 5-deoxy-5-iodo-1,2-0-isopropylidene- -d-xylofuranose (30). A solution of 1.14 grams of 30 in pyridine (8.0 ml.) was shaken at room temperature with silver fluoride (2.0 grams). The reaction was slower than with the corresponding 5-tosylate (22) and was complete after 72 hours. The reaction mixture was processed as described above to give a pale yellow sirup which contained, in addition to 28, three minor components. Distillation afforded pure material (0.4 grams, 75%) identical with material prepared as above. 

Methyl 5-deoxy-2,3-0-isopropylidene l3-T>-erythro-pent-4-enofurano-side (43). A solution of methyl 5-deoxy-5-iodo-2,3-0-isopropylidene-/ -D-ribofuranoside (42) (30) (1.0 grams) in pyridine (10 ml.) was shaken for 7 hours at room temperature with anhydrous silver fluoride (1.5 grams). Isolation of the product as described previously afforded the 4-ene (43) as a sirup (414 mg., 70%) which distilled at 40°C. (bath) at 0.1 mm. G.l.c. showed the presence of a major component (95%) together with 5% of another component which was not investigated. [ ]D21 + 26.3° (c, 2.3). Anal Calcd. for C9H1404 C, 58.05 H, 7.6. Found C, 57.9 H, 7.7. 

Silver fluoride is soluble. Therefore, no precipitate forms as Ag ions are added to a solution of F ions. 

Silver(I) does not disproportionate in aqueous solution and, in almost all its compounds, silver has oxidation number +1. Apart from silver nitrate, AgN03, and silver fluoride, silver salts are generally only sparingly soluble in water. Silver nitrate is the most important compound of silver and the starting point for the manufacture of silver halides for use in photography. 

Fluorination with Silver Fluoride from Glycosyl Bromide [17] A mixture of 2,3,4,6-tetra- O-acetyl-a-D-glucopyranosyl bromide (5 g) and anhydrous silver fluoride (5 g) in dry acetonitrile (25 ml) was shaken under argon overnight. The resulting solution was filtered and aqueous sodium chloride was added to precipitate any silver ions from the solution. The mixture was filtered and concentrated to a syrup that was... 

In reactions in which HC1, HBr, or HI are evolved there is a convenient way of detecting and following the course of the reaction. Gas will be evolved and a bead of silver nitrate solution in a small loop of nichrome wire placed in this gas stream will become opaque, if these gases are present. Hydrogen fluoride will not do this since silver fluoride is very soluble in water. If a simple test for hydrogen fluoride is desired, a similar bead of calcium chloride will serve very well. 

Silver fluoride is prepared by slowly dissolving excess silver oxide in hydrofluoric acid (50%) over 24 h. The filtered solution is evaporated to dryness in vacuo at 35 °C and then heated to 60 °C for 1 h. The yellow solid as stored over P205 away from light and powdered before use. 

A mixture of Re(CO)5Br dissolved in 8 mL of fluorobenzene and finely divided and freshly prepared silver fluoride (30 mg, 0.24 mmol, two-fold excess) is stirred in a glass vessel at room temperature for 2 h. The solution is filtered to remove the precipitated silver bromide and excess silver fluoride. The filtrate is heated to reflux at 90 to 100°C for 5 h, cooled to room temperature, and the solvent is removed under vacuum to give the yellow product. Yield 44 mg, 0.036 mmol (75% yield). This can be recrystallized from a diethyl ether solution into which fluorobenzene is allowed to diffuse and dried in vacuo to give needle or prismatic crystals. 

ZnF2 (aq.). Petersen1 measured the heat of the reaction of aqueous zinc chloride with solid silver fluoride to be 31.84. Mulert1 measured the heat of solution of ZnO in aqueous (20%) HF to be 21.82. See also Jellinek and Rudat.1... 

A solution of S-iodomethyl-6a,9a-difluoro-lip-hydroxy-16a-methyl-3-oxo-17a-propionyloxyandrosta-l,4-diene-17p-carbothioate (310 mg) in acetonitrile (10 ml) was stirred with silver fluoride (947 mg) for 3 days at room temperature in the dark. Ethyl acetate (100 ml) was added and the mixture was filtered through kieselguhr. The filtrate was washed successively with 2 N hydrochloric acid, water, saturated brine, then dried. The solvent was removed and the residue was subjected to column chromatography in chloroform then chloroform-acetone (19 1). The product was eluted with ethyl acetate and crystallised on concentration of the solution to give S-fluoromethyl 6a,9a-difluoro-lip-hydroxy-16a-methyl-3-oxo-17a-propionyloxyandrosta-l,4-diene-17p-carbothioate (0.075 g) melting point 272-273°C (dec.), [a]D= +30° (c 0.35). 

Diphenyl Tellurium Difluoride6 A mixture of 15 ml of dry toluene and 2 g (16 mmol) of silver fluoride is heated to reflux, and 1.3 g (3 mmol) of diphenyl tellurium diiodide are added in portions to the refluxing silver fluoride suspension. Additional diiodide is added after the reddish color of the solution has disappeared. The hot solution is filtered under aspirator vacuum, The filtrate deposits the crystalline product on cooling. The difluoride is filtered off, washed with toluene, and recrystallized from benzene the pure product has m.p. 154°. 

Fluoride Place 5 g of sample, 25 mL of water, 50 mL of sulfuric acid, 5 drops of a 1 2 silver nitrate solution, and a few glass beads in a 250-mL distilling flask connected to a condenser and carrying a thermometer and a capillary tube,... 

If an evaporator was used, transfer the concentrate to a Teflon beaker. Assay the bromate concentration and add with stirring enough saturated silver fluoride to provide a 0.1-0.2 M excess after precipitation of silver bromate. Centrifuge. Wash the precipitate with 0.1 M silver fluoride and discard it. Pass the supernatant solution and washings under suction through an extra-fine Teflon filter disk on a polyethylene Buchner funnel. 

Silver nitrate solution no precipitate, since silver fluoride is soluble in water. 

The reagent (a manganese(II) nitrate-silver nitrate solution containing potassium fluoride) is prepared as follows. Dissolve 2 87 g manganese(II) nitrate and 1-69 g silver nitrate in 100 ml water, add a drop of dilute alkali and filter the solution from the black precipitate. Treat the filtrate with a solution of 3 5 g potassium fluoride in 50 ml water a white precipitate will form which on heating becomes grey and black. Boil, filter, and use the clear solution as the reagent. 

Add CaCl2 solution (equal in volume to that of the solution) and allow to stand for several minutes. A white precipitate indicates fluoride, oxalate, phosphate, arsenate, and tartrate t a precipitate which separates on boiling for 1-2 minutes is citrate. Of these only oxalate and fluoride are insoluble in dilute acetic acid. Hence extract the white precipitate with dilute acetic acid and filter. A residue (R) insoluble in dilute acetic acid, indicates oxalate and/or fluoride. Exactly neutralize the acetic acid solution by adding sodium hydroxide solution from a dropper and testing with an indicator paper or solution (bromothymol blue or nitrazine yellow is suitable) a white precipitate indicates the presence of phosphate, arsenate, and/or tartrate. The precipitate often separates slowly. Add a little silver nitrate solution to the suspension or solution a yellow precipitate indicates the presence of phosphate a brownish-red precipitate indicates arsenate or arsenate plus phosphate. 

Silver fluoride, AgF.—Evaporation in vacuum of a solution of silver oxide in hydrofluoric acid yields the fluoride in the form of an amorphous, yellow mass, of density 2 5-852 at 15-5° C. At red heat it melts to a black liquid, which on cooling solidifies to a crystalline mass.3 It is very soluble in water, its solubility at 15-5° C. being 181-8 grams per 100 grams of water. The solution has a neutral reaction. In its solubility the fluoride presents a marked contrast to the other silver halides. The anhydrous salt can absorb 844 times its volume of ammonia. 

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