Silver acetate

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.

Synthesis and structure

Silver acetate can be synthesized by the reaction of acetic acid and silver carbonate at 45â€"60 °C. After allowing cooling to room temperature, the solid product precipitates.

2 CH₃CO₂H + Ag₂CO₃ â†' 2 AgO₂CCH₃ + H_{2b>O + CO2}

It 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.

Reactions

Carbonylation

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 â†' [R₂N]₂CO + 2 HOAc + 2 Ag

Hydrogenation

A solution of silver acetate in pyridine absorbs hydrogen, producing metallic silver:

2 CH₃CO₂Ag + H₂ â†' 2 Ag + 2 CH₃CO₂H

Direct 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.

References

Further reading

• F. H. MacDougall, and S. Peterson (1947). "Equilibria in Silver Acetate Solutions". The Journal of Physical Chemistry 51 (6): 1346â€"1361. doi:10.1021/j150456a009. 

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