Silver® carbonate

Alternate Names silver carbonate, disilver carbonate, Fetizon s reagent. 

Solubility insoluble in water, soluble in nitric acid, liquid ammonia. 

Form Supplied in faint green to dark green and faint brown to dark brown powder. 

Preparative Method by reaction of silver(I) nitrate with sodium carbonate in deionized water.  

Handling, Storage, and Precautions light sensitive. Causes serious eye damage. Very toxic to aquatic life, may cause long-term adverse effects in the aquatic environment. In case of contact with eyes, rinse with copious amounts of water. Must be disposed of as hazardous waste. 

Oxidations with Silver (Silver Carbonate and Silver Oxide) 

Silver Carbonate. Silver carbonate (Ag2C03) is not a powerful oxidizing agent but it is extremely useful in organic chemistry. Rapoport et al. were probably the first to use silver carbonate for the oxidation of alcohols to carbonyl derivatives. Rapoport refluxed codeine (108) with silver carbonate in benzene and obtained a 75% yield of codeinone (109).In later work King et al. oxidized codeine with silver carbonate in refluxing toluene or xylene and obtained an 85% yield of 109 with a much shorter reaction time.  

Fetizon proposed a mechanism by which involved adsorption of the alcohol on silver carbonate gave a species such as 110. One-electron transfer via the silver ion in 111 liberated the protonated carbonyl and carbonic acid (see 112), which decomposed to carbon dioxide and water.l This mechanism involved four 

Reversible adsorption of alcohol on the surface of the oxidizing medium with the electron of oxygen forming a coordinated covalent bond with the silver ions. 

Oxidation of the C—H bond so the HCOH group is coplanar and perpendicular to the silver carbonate/Celite surface. 

Ag2COa can be prepared in two forms described [757] as active , readily decomposed at 439 K, and inactive , which achieved the same rate of decomposition only at 593 K. Reaction yielded Ag20 and C02 or, at higher temperature ( 520 K) Ag, 02 and C02. 

The high reactivity of the active form of Ag2C03 is attributed to the retention of water, incorporated during preparation, in the form of the ions HCOj and OH , with corresponding cation vacancies (VAg+), viz. 

Such defects facilitate movement of C02 within the crystal by transfer from HCOj to OH and of Ag+ in the cation vacancies. This interpretation is supported [758,759] by the observed increase in reactivity resulting from doping of Ag2C03 with Cd2+, Y3+ or Gd3+, where incorporation of the additive is accompanied by the creation of cation vacancies. 

Differentiation between the two forms of Ag2C03 is not easy and, from the many methods used, electron spin resonance spectroscopy and thermal analysis have been most successfully applied [757]. The imperfections mentioned above occur in the low temperature decomposition product and are identified as being responsible for enhanced activity in readsorbing C02. Annealing of the residue removes these defects and reduces the reversibility of reaction. 

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Coesite. Coesite, the second most dense (3.01 g/cm ) phase of silica, was first prepared ia the laboratory by heating a mixture of sodium metasibcate and diammonium hydrogen phosphate or another mineraliser at 500—800°C and 1.5—3.5 GPa (14,800—34,540 atm). Coesite has also been prepared by oxidation of silicon with silver carbonate under pressure (67). The stmcture is monoclinic = 717 pm, Cg = 1.238 pm, and 7 = 120°. 

Silver Carbonate. Silver carbonate, Ag2C02, is produced by the addition of an alkaline carbonate solution to a concentrated solution of silver nitrate. The pH and temperature of the reaction must be carefully controlled to prevent the formation of silver oxide. A suspension of Ag2C02 is slightly basic because of the extensive hydrolysis of the ions present. Heating soHd Ag2C02 to 218°C gives Ag20 and CO2. 

Silver Fluoride. Silver fluoride, AgF, is prepared by treating a basic silver salt such as silver oxide or silver carbonate, with hydrogen fluoride. Silver fluoride can exist as the anhydrous salt, a dihydrate [72214-21-2] (<42° C), and a tetrahydrate [22424-42-6] (<18° C). The anhydrous salt is colorless, but the dihydrate and tetrahydrate are yellow. Ultraviolet light or electrolysis decomposes silver fluoride to silver subfluoride [1302-01 -8] Ag2p, and fluorine. 

When heated to 100°C, silver oxide decomposes into its elements, and is completely decomposed above 300°C. Silver oxide and sulfur form silver sulfide. Silver oxide absorbs carbon dioxide from the air, forming silver carbonate. 

Silver Selenate. Silver selenate, Ag2Se04, is prepared from silver carbonate and sodium selenate (see Seleniumand selenium compounds). 

Silver carbonate, alone or on CeHte, has been used as a catalyst for the oxidation of methyl esters of D-fmctose (63), ethylene (64), propylene (65), trioses (66), and a-diols (67). The mechanism of the catalysis of alcohol oxidation by silver carbonate on CeHte has been studied (68). 

The reaction is sensitive to the presence of metallic silver at the start, indicating autocatalysis, and to the presence of silver carbonate, which was accidentally present in some investigations. 

Acknowledgment The authors wish to express their gratitude to Dr. J. Edwards of Syntex Research who provided the experimental procedure utilizing silver carbonate on Celite. We are also indebted to the Synthetic Chemical Research Department of Merck Sharp Dohme Research Laboratories for providing time to complete this review and also to Miss Joanna Mohr for her patience and care in preparing the manuscript. 

Preliminary experiments on the coupling of the chloride (lb) with digitoxigenin (3/ ,14,/ -dihydroxy-5/ -card-20(22)-enolide) in the presence of silver carbonate, led to gross decomposition of the halide, and it was suspected that, under the conditions of the experiments, the silver carbonate was causing elimination of hydrogen chloride. When, however, digitoxigenin was treated with an excess of lb in a small volume of... 

Methyl 2-deoxy-39496-tri-0-p-nitrobenzoyl-p-T>- yxo-hexoside. A solution of 370 mg. of 2-deoxy-3,4,6-tri-0-p-nitrobenzoyl- -D-Zyxo-hexosyl bromide (5) in 15 ml. of dry dichloromethane is added to a stirred suspension of 500 mg. of silver carbonate in 100 ml. of absolute methanol. The mixture is stirred for 20 hours and filtered the silver salts are washed several times with warm dichloromethane. The combined filtrate and washings are evaporated to dryness under diminished pressure, and the residue is recrystallized five times from ether-dichloromethane, giving 61% of pure product, having m.p. 173°-174°C. and [ ]D + 36° in chloroform. 

Deoxy-D-ribo-hexono-l,4-lactone. To 286 mg. of 2-deoxy-D-ribo-hexose in 4 ml. of water is added 0.3 ml. of bromine. The solution is kept overnight at 37°C. and is then aerated to remove the excess bromine. Silver carbonate (1.5 grams) is added and the mixture is filtered. The clear filtrate is stirred with 5.4 grams of Dowex-50W X8 (H+) ion-exchange resin, decolorized, and filtered, and the filtrate is evaporated... 

The successful implementation of this strategy is shown in Scheme 4. In the central double cyclization step, the combined action of palladium(n) acetate (10 mol %), triphenylphosphine (20 mol %), and silver carbonate (2 equiv.) on trienyl iodide 16 in refluxing THF results in the formation of tricycle 20 (ca. 83 % yield). Compound 20 is the only product formed in this spectacular transformation. It is noteworthy that the stereochemical course of the initial insertion (see 17—>18) is guided by an equatorially disposed /-butyldimethylsilyl ether at C-6 in a transition state having a preferred eclipsed orientation of the C-Pd a bond and the exocyclic double bond (see 17). Insertion of the trisubstituted cycloheptene double bond into the C-Pd bond in 18 then gives a new organopal-... 

Disarmed as well as armed (see Section V and Scheme 9) phenyl selenoglycosides are reported to be activated by silver triflate in the presence of potassium or silver carbonate in the presence of armed ethyl thioglycoside acceptors, to produce ethyl thiodisaccharides in excellent yields. 

The complex 65 was synthesized by reaction of the imidazolinium salt with the precursor ruthenium complex 67 (catalytically inactive) in the presence of silver carbonate (Scheme 42). The complex being air-stable and stable on silicagel was isolated in 52% yield after chromatography. The diastereomeric and enantiomeric purity of 65 was determined by HPLC analysis and found to be above 98% (de and ee). The molecular structure was determined by X-ray analysis and showed the unusual twist geometry of this complex. 

Silver bromide Silver chloride Silver perchlorate Silver cyanide Silver fluoride Silver iodide Silver permar>gate Silver nitrate Silver carbonate Silver oxide Silver sulphate Silver sulphide Silver phosphate... 

Despite the presence of a nonparticipating group at C-2, condensation of3,4,6-tri-0-acetyl-2-(anisylideneamino)-2-deoxy-a-D-glucopyranosyl bromide (159) with 160 in the presence of silver carbonate and sodium sulfate gave N-(benzyloxycarbonyl)-3-0-[3,4,6-tri-0-acetyl-2-(anisyli-deneamino)-2-deoxy-/ -D-glucopyranosyl]-L-threonine methyl ester125 (161). 

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