Formula AgC2H3O2 Density 3.26 g/cm³ | Molar mass 166.91 g/mol Boiling point 220 °C | |
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Appearance white to slightly grayish powder; slightly acidic odor | ||
Silver acetate is an inorganic compound with the empirical formula CH3CO2Ag (or AgC2H3O2). It is a photosensitive, white, crystalline solid. It is a useful reagent in the laboratory as a source of silver ions lacking an oxidizing anion. It has been used in some antismoking drugs.
Contents
Synthesis and structure
Silver acetate can be synthesized by the reaction of acetic acid and silver carbonate at 45–60 °C. After allowing cooling to room temperature, the solid product precipitates.
2 CH3CO2H + Ag2CO3 → 2 AgO2CCH3 + H2O + CO2It can also be precipitated from concentrated aqueous solutions of silver nitrate by treatment with a solution of sodium acetate.
The structure of silver acetate consists of 8-membered Ag2O4C2 rings formed by a pair of acetate ligands bridging a pair of silver centres.
Thermal Decomposition
Solid silver acetate decomposes with heat to make silver particles and various gases, depending on the atmosphere present, and decomposes at slightly lower temperatures with increasing humidity. In air, the reaction mainly goes by the following:
4 CH3CO2Ag + 7 O2 → 4 Ag + 8 CO2 + 6 H2OCarbonylation
Silver acetate, when combined with carbon monoxide (CO), can induce the carbonylation of primary and secondary amines. Other silver salts can be used but the acetate gives the best yield.
2 R2NH + 2 AgOAc + CO → [R2N]2CO + 2 HOAc + 2 AgHydrogenation
A solution of silver acetate in pyridine absorbs hydrogen, producing metallic silver:
2 CH3CO2Ag + H2 → 2 Ag + 2 CH3CO2HDirect ortho-arylation
Silver acetate is a useful reagent for direct ortho-arylation (to install two adjacent substituents on an aromatic ring) for of benzylamines and N-methylbenzylamines. The reaction is palladium-catalized and requires a slight excess of silver acetate. This reaction is shorter than previous ortho-arylation methods.
Oxidative dehalogenation
Silver acetate can be used to convert certain organohalogen compounds into alcohols. It may be used, in spite of its high cost, in instances where a mild and selective reagent is desired.
Woodward cis-hydroxylation
Silver acetate in combination with iodine forms the basis of the Woodward cis-hydroxylation. This reaction selectively converts an alkenes into a cis-diols.
Uses
In the health field, silver acetate-containing products have been used in gum, spray, and lozenges to deter smokers from smoking. The silver in these products, when mixed with smoke, creates an unpleasant metallic taste in the smoker's mouth, thus deterring them from smoking. Lozenges containing 2.5 mg of silver acetate showed "modest efficacy" on 500 adult smokers tested over a three-month period. However, over a period of 12 months, prevention failed. In 1974, silver acetate was first introduced in Europe as an over-the-counter smoking-deterrent lozenge (Repaton) and then three years later as a chewing gum (Tabmint).
Safety
The LD50 of silver acetate in mice is 36.7 mg/kg. Low doses of silver acetate in mice produced hyper-excitability, ataxia, central nervous system depression, labored breathing, and even death. The U.S. FDA recommends that silver acetate intake be limited to 756 mg over a short period of time; excessive intake may cause argyria.