azido

Azido is the adjective used in chemistry to describe compounds bearing the azido group. The azido group consists of a terminal –N3 moiety, which can occur as the azide ion N3− or as a substituent attached to a carbon-containing framework (R–N3). The group is linear with three nitrogens and participates in resonance among several structures, imparting distinctive reactivity. The azide ion is a relatively weak base and a good nucleophile, forming salts such as sodium azide (NaN3) and silver azide (AgN3). Organic azides (R–N3) are prepared by azidation of electrophiles such as alkyl or acyl derivatives and are common intermediates in organic synthesis.

In synthetic chemistry, azido groups are central to click chemistry, especially the copper(I)-catalyzed azide–alkyne cycloaddition (CuAAC), which produces 1,4-disubstituted 1,2,3-triazoles with high reliability and selectivity. Organic azides are also used in the preparation of heterocycles, peptide labeling, polymer functionalization, and pharmaceutical development. The term azido is used as a prefix in systematic nomenclature to indicate the presence of the azido group.

Safety and handling: many azides are toxic and some metal azides are explosive or shock-sensitive; care must be taken to avoid friction, impact, and heat, and to control storage conditions and impurities.