Silver acetylide

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Silver acetylide
Wireframe model of silver acetylide
Silver acetylide3.jpg
Names
Preferred IUPAC name
Disilver acetylide
Systematic IUPAC name
Disilver(1+) ethyndiide
Other names
Argentous ethyndiide

Argentous percarbide
Silver(1+) dicarbon
Silver ethynide

Silver percarbide
Identifiers
3D model (Jmol)
Properties
C2Ag2
Molar mass 239.76 g·mol−1
Appearance gray or white solid
Melting point 120 °C (248 °F; 393 K)
Boiling point decomposes
insoluble
Hazards
Main hazards High Explosive, Toxic
Flash point 77 °C (171 °F; 350 K)
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

Silver acetylide is an inorganic chemical compound with the formula Ag2C2, a metal acetylide. The compound can be regarded as a salt of the weak acid, acetylene. The salt's anion consists of two carbon atoms linked by a triple bond. The alternate name "silver carbide" is rarely used, although the analogous calcium compound CaC2 is called calcium carbide.

Pure silver acetylide is a heat- and shock-sensitive high explosive with the unusual property that on ignition it does not evolve any gas:

Ag
2
C
2
(s) → 2 Ag (s) + 2 C (s)

A common misconception about the "silver acetylide" used in commercial explosives is that it explodes without the evolution of gaseous products and that its chemical formula is Ag
2
C
2
. In reality, it is a double salt with the silver salt it was produced from, usually silver nitrate.[1] The anion of the parent compound acts as the oxidizer in the decomposition reaction.

The detonation velocity of the mixture silver acetylide: silver nitrate is 3460 m/s.[2] That of pure silver acetylide is 4000 m/s.

Synthesis[edit]

Silver acetylide can be produced by passing acetylene gas through a solution of silver nitrate:[3]

2 AgNO
3
(aq) + C
2
H
2
(g) → Ag
2
C
2
(s) + 2 HNO
3
(aq)

The reaction product is a greyish to white precipitate. This is the same synthesis from Berthelot in which he first found silver acetylide in 1866.[4]

Silver acetylide can be formed on the surface of silver or high-silver alloys, e.g. in pipes used for transport of acetylene, if silver brazing was used in their joints.

Solubility[edit]

Silver acetylide is not soluble in water and is not appreciably soluble in any other solvent.

References[edit]

  1. ^ "Silver Acetylide (Double Salts)". Williestop.tripod.com. Retrieved 2013-01-29. 
  2. ^ Sam Barros. "Acetylide Explosives Synthesis". Powerlabs.org. Retrieved 2013-01-29. 
  3. ^ G.-C. Guo; Q.-G. Wang; G.-D. Zhou; T. C. W. Mak (1998). "Synthesis and characterization of Ag2C2·2AgClO4·2H2O: a novel layer-type structure with the acetylide dianion functioning in a 6112222 bonding mode inside an octahedral silver cage". Chem. Commun. (3): 339–340. doi:10.1039/a708439k. 
  4. ^ M. P. Berthelot (1866). "Ueber eine neue Klasse zusammengesetzter metallhaltiger Radicale (A new class of combined metallic radicals)". Annalen der Chemie. 138 (2): 245–253. doi:10.1002/jlac.18661380215.