Many inorganic azides can be prepared directly or indirectly from sodium azide. For example, lead azide, used in detonators, may be prepared from the metathesis reaction between lead nitrate and sodium azide. An alternative route is direct reaction of the metal with silver azide dissolved in liquid ammonia.[3] Some azides are produced by treating the carbonate salts with hydrazoic acid.
Azide salts can decompose with release of nitrogen gas. The decomposition temperatures of the alkali metal azides are: NaN3 (275 °C), KN3 (355 °C), RbN3 (395 °C), and CsN3 (390 °C). This method is used to produce ultrapure alkali metals:[4]
2 MN3heat→2 M + 3 N2
Protonation of azide salts gives toxic hydrazoic acid in the presence of strong acids:
Many inorganic covalent azides (e.g., chlorine, bromine, and iodine azides) have been described.[5]
The azide anion behaves as a nucleophile; it undergoes nucleophilic substitution for both aliphatic and aromatic systems. It reacts with epoxides, causing a ring-opening; it undergoes Michael-like conjugate addition to 1,4-unsaturated carbonyl compounds.[1]
Azides can be used as precursors of the metal nitrido complexes by being induced to release N2, generating a metal complex in unusual oxidation states (see high-valent iron).
Azides decompose with nitrite compounds such as sodium nitrite when acidified. This is a method of destroying residual azides, prior to disposal.[6] In the process, nitrogen, nitrogen oxides, and hydroxides are formed:
About 251 tons of azide-containing compounds are produced annually, the main product being sodium azide.[7]Sodium azideNaN3 is the propellant in automobile airbags. It decomposes on heating to give nitrogen gas, which is used to quickly expand the air bag:[7]
2 NaN3 → 2 Na + 3 N2
Heavy metal azides, such as lead azide, Pb(N3)2, are shock-sensitive detonators which decompose to the corresponding metal and nitrogen, for example:[8]
Azides are explosophores[9][10] and poisons. Sodium azide is as toxic as sodium cyanide (with an oral LD50 of 27 mg/kg in rats) and can be absorbed through the skin. Heavy metal azides, such as lead azide are primaryhigh explosivesdetonable when heated or shaken. Heavy-metal azides are formed when solutions of sodium azide or HN3 vapors come into contact with heavy metals or their salts. Heavy-metal azides can accumulate under certain circumstances, for example, in metal pipelines and on the metal components of diverse equipment (rotary evaporators, freezedrying equipment, cooling traps, water baths, waste pipes), and thus lead to violent explosions.
^Müller, Thomas G.; Karau, Friedrich; Schnick, Wolfgang; Kraus, Florian (2014). "A New Route to Metal Azides". Angewandte Chemie. 53 (50): 13695–13697. doi:10.1002/anie.201404561. PMID24924913.
^Dönges, E. (1963). "Alkali Metals". In Brauer, G. (ed.). Handbook of Preparative Inorganic Chemistry. Vol. 1 (2nd ed.). NY: Academic Press. p. 475.
