azides

Azides are compounds containing the azide group, N3−, or the organic azide moiety R−N3. The azide anion is linear and resonance-stabilized, described by forms such as [-N=N+=N−] and [-N≡N+-N−]. Organic azides, R−N3, are widely used as reactive intermediates in synthesis. Inorganic azides such as sodium azide NaN3 and potassium azide KN3 are typically white crystalline solids; many metal azides (for example AgN3, Pb(N3)2) are shock-sensitive explosives.

In synthesis, azides are versatile precursors. Alkyl and aryl halides can undergo SN2 substitution with sodium azide to give alkyl or aryl azides, which can be reduced to amines (Staudinger reduction) or transformed into other nitrogen-containing motifs. Acidification can generate hydrazoic acid HN3, a highly toxic gas, highlighting safety concerns. In organic chemistry, the azide group is central to the Cu-catalyzed Huisgen 1,3-dipolar cycloaddition with alkynes to form 1,4-disubstituted 1,2,3-triazoles, a foundational reaction in click chemistry. Azides also participate in Curtius and Schmidt rearrangements, converting acyl azides or azide derivatives into amines or isocyanates.

Safety and handling: Azides can be energetic and sensitive to shock, heat, and friction, particularly metal azides. Hydrazoic acid forms under acidic conditions. Proper storage and handling require avoiding shock, heat, acids, and contamination with heavy metals, with reactions performed on appropriate scales and under protective measures.

Applications and occurrence: Sodium azide has been used in airbag gas generators and as a precursor to various organic and inorganic azides; metal azides are used as detonators and primers in pyrotechnics. In chemistry, azides are valuable building blocks for nitrogen-containing compounds and materials.