Silver acetate

Silver acetate
Other names Acetic acid, silver (1+) salt
Identifiers
CAS number	563-63-3 Y
PubChem	11246
ChemSpider	10772 Y
UNII	19PPS85F9H Y
Jmol-3D images	Image 1
SMILES CC(=O)[O-].[Ag+]
InChI InChI=1S/C2H4O2.Ag/c1-2(3)4;/h1H3,(H,3,4);/q;+1/p-1 Y Key: CQLFBEKRDQMJLZ-UHFFFAOYSA-M Y InChI=1/C2H4O2.Ag/c1-2(3)4;/h1H3,(H,3,4);/q;+1/p-1 Key: CQLFBEKRDQMJLZ-REWHXWOFAJ
Properties
Molecular formula	AgC2H3O2
Molar mass	166.91 g/mol
Appearance	white to slightly grayish powder slightly acidic odor
Density	3.26 g/cm3, solid
Boiling point	decomposes at 220 °C
Solubility in water	1.02 g/100 mL(20 °C)
Hazards
EU classification	not listed
NFPA 704	0 1 0
Y (verify) (what is: Y/N?) Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

Silver acetate (AgC₂H₃O₂) is a photosensitive, white crystalline substance commonly used as a pesticide. It also produces a repulsive metallic taste when combined with cigarette smoke, so it is used in chewing gum and lozenges to aid the cessation of smoking.

Isolation

Silver acetate, the silver salt form of acetic acid, has been isolated from citric acid-forming strains of the fungi Aspergillus niger. From A. niger grown on glucose media and inorganic salts, acetic acid was collected, treated with sodium hydroxide, and evaporated to a small volume. After neutralization with nitric acid, the solution was treated with silver nitrate. A soft precipitate was filtered off, washed free of nitric acid, and dried in a vacuum. This soft precipitate was assumed to be silver acetate.

Synthesis

The silver acetate salt can be synthesized via the reaction of acetic acid and silver carbonate at 45–60 °C. After allowing cooling to room temperature, the product was filtered off.

C₂H₃O₂ + Ag₂CO₃ ⇒ AgC₂H₃O₂

It can also be prepared from aqueous silver nitrate and an acetate ion.

Properties

Solubility

Silver acetate is a moderately soluble crystalline silver source. 100 mL of water can dissolve just over one gram of silver acetate at 20 °C.

AgC₂H₃O₂(s) ↔ Ag⁺(aq) + C₂H₃O₂^- (aq)

Stability

Silver acetate solutions are unstable to light.

Reactions

Formation of a Precipitate

The precipitate is prepared by mixing two salts, one with Ag⁺ and another with C₂H₃O₂^- (i.e. AgNO₃ and NaC₂H₃O₂).

Ag (aq) + C₂H₃O₂^- (aq) ↔ AgC₂H₃O₂ (s)

Carbonylation

Silver acetate, when combined with carbon monoxide (CO), can cause the carbonylation (the formation of a C=O bond) of primary and secondary amines at room temperature. Many silver salts can be used (i.e. AgOAc, AgNO₃, AgCl, AgCN), but silver acetate gives the best product yield.

Primary Amine: RNH₂ + AgOAc + CO ⇒ RNHCONHR

Secondary Amine: R₂NH + AgOAc + CO ⇒ R₂N(CO)₂NR₂

Metallic silver and acetic acid are also formed as byproducts of these reactions.

Hydrogenation

Silver acetate, when in a solution of pyridine, absorbs hydrogen and is reduced to metallic silver.

Quinolone solutions of silver acetate absorb hydrogen rapidly at 100 °C to form metallic silver.

Direct ortho-arylation

Silver acetate can be used in a method for direct ortho-arylation (in which the two substituents on an aromatic ring occupy adjacent carbons) of benzylamines and N-methylbenzylamines. The reaction is palladium-catalized and requires a slight excess of silver acetate.

(C₆H₅)NHMe + (C₆H₅)I ⇒(C₆H₅Me)₂(C₆H₃)CH₂N(COMe)Me

This reaction presents a much shorter method than previous ortho-arylation methods (i.e. required picolylamide directing group; only successful for primary amine derivatives).

Uses

In industry, silver acetate has been used in the preparation of highly reflective, conductive silvered polymer films. It also could be used to catalyze cycloaddition reactions of isocyanatoacetates.

In the health field, silver acetate-containing products have been used in such products as gum, spray, and lozenges to deter smokers from smoking. The silver in these products, when mixed with smoke, creates a terrible metallic taste in the smoker's mouth, thus deterring them from smoking. Research has shown that lozenges containing 2.5 mg of silver acetate showed "modest efficacy" on 500 adult smokers tested over a three-month period. However, long-term (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).

In nanotechnology, silver acetate has been loaded into the tube lumen (the cavity within the tube) of halloysites (a naturally available aluminosilicate clay) under reduced pressure, washing separation, and heating. This tube has been used as a well-dispersed antimicrobial additive in plastic composites.

Silver Acetate dissolved into ammonia has been used by researchers at the University of Illinois as a conductive ink for use in printable circuits. The process was a breakthrough in that it allowed for printing at lower temperatures and on a wider variety of plastic bases materials.

Safety

The LD₅₀ (lethal dose) of silver acetate in mice is 36.7 mg/kg (low LD₅₀ means very toxic). Low doses of silver acetate in these mice produced hyper-excitability, ataxia, central nervous system depression, labored breathing, and even death. The FDA recommends that silver acetate intake be limited to 756 mg over a short period of time; excessive intake may cause argyria.

Further reading

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