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Silver azide

Silver azide
Silver-azide-high-T-single-layer-3D-vdW.png
Names
IUPAC name
Silver(I) azide
Other names
Argentous azide
Identifiers
3D model (JSmol)
ChemSpider
ECHA InfoCard 100.034.173 Edit this at Wikidata
UNII
CompTox Dashboard (EPA)
Properties
Chemical formula
 AgN3
Molar mass 149.888 g/mol
Appearance colorless solid
Density 4.42 g/cm3, solid
Melting point 250 °C (482 °F; 523 K) explosive
Boiling point decomposes
Solubility in other solvents 2.0×10−8 g/L
Structure
Crystal structure
 Orthorhombic oI16[1]
Ibam, No 72
Hazards
Main hazards Very toxic, explosive
NFPA 704 (fire diamond)
NFPA 704 four-colored diamond
0
3
4
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).

Silver azide is the chemical compound with the formula AgN3. This colorless solid is a well-known explosive.

Structure and chemistry

Silver azide can be prepared by treating an aqueous solution of silver nitrate with sodium azide.[2] The silver azide precipitates as a white solid, leaving sodium nitrate in solution.

AgNO
3 (aq) + NaN
3 (aq) → AgN
3 (s) + NaNO
3 (aq)

X-ray crystallography shows that AgN3 is a coordination polymer with square planar Ag+ coordinated by four azide ligands. Correspondingly, each end of each azide ligand is connected to a pair of Ag+ centers. The structure consists of two-dimensional AgN3 layers stacked one on top of the other, with weaker Ag–N bonds between layers. The coordination of Ag+ can alternatively be described as highly distorted 4 + 2 octahedral, the two more distant nitrogen atoms being part of the layers above and below.[3]

Silver-azide-high-T-single-layer-3D-balls.png
Silver-azide-high-T-layer-stacking-3D-balls.png
Silver-azide-high-T-Ag-coordination-3D-balls-A.png
Silver-azide-high-T-N-coordination-3D-balls-B.png
Part of a layer
Layer stacking
4 + 2 coordination of Ag+
2 + 1 coordination of N in N−
3

In its most characteristic reaction, the solid decomposes explosively, releasing nitrogen gas:

2 AgN
3 (s) → 3 N
2 (g) + 2 Ag (s)

The first step in this decomposition is the production of free electrons and azide radicals; thus the reaction rate is increased by the addition of semiconducting oxides.[4] Pure silver azide explodes at 340 °C, but the presence of impurities lowers this down to 270 °C.[5] This reaction has a lower activation energy and initial delay than the corresponding decomposition of lead azide.[6]

Safety

AgN3, like most heavy metal azides, is a dangerous primary explosive. Decomposition can be triggered by exposure to ultraviolet light or by impact.[2] Ceric ammonium nitrate is used as an oxidising agent to destroy AgN
3 in spills.[5]

See also

  • Silver nitride

References

  1. ^ Marr H.E. III.; Stanford R.H. Jr. (1962). "The unit-cell dimensions of silver azide". Acta Crystallographica. 15 (12): 1313–1314. doi:10.1107/S0365110X62003497.
  2. ^ a b Robert Matyas, Jiri Pachman (2013). Primary Explosives (1st ed.). Springer. p. 93. ISBN 978-3-642-28435-9.[1]
  3. ^ Schmidt, C. L. Dinnebier, R.; Wedig, U.; Jansen, M. (2007). "Crystal Structure and Chemical Bonding of the High-Temperature Phase of AgN3". Inorganic Chemistry. 46 (3): 907–916. doi:10.1021/ic061963n. PMID 17257034.
  4. ^ Andrew Knox Galwey; Michael E. Brown (1999). Thermal decomposition of ionic solids (vol.86 of Studies in physical and theoretical chemistry. Elsevier. p. 335. ISBN 978-0-444-82437-0.
  5. ^ a b Margaret-Ann Armour (2003). Hazardous laboratory chemicals disposal guide, Environmental Chemistry and Toxicology (3rd ed.). CRC Press. p. 452. ISBN 978-1-56670-567-7.
  6. ^ Jehuda Yinon; Shmuel Zitrin (1996). Modern Methods and Applications in Analysis of Explosives. John Wiley and Sons. pp. 15–16. ISBN 978-0-471-96562-6.
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