Trinitrogen

Trinitrogen also known as the azide radical is an unstable molecule composed of three nitrogen atoms. Two arrangements are known: a linear form with double bonds and charge transfer, and a cyclic form. Both forms are highly unstable, though the linear form is the more stable of the two.^[1] More-stable derivatives exist, such as when it acts as a ligand, and it may participate in azido nitration, which is a reaction between sodium azide and ammonium cerium nitrate.^[2][3]

Trinitrogen

Names
Other names Azide radical Triazirene (cyclic) Triazadienyl
Identifiers
CAS Number	linear: 12596-60-0
3D model (JSmol)	linear: Interactive image cyclic: Interactive image
ChEBI	linear: CHEBI:29448
ChemSpider	linear: 5256999
Gmelin Reference	770
PubChem CID	linear: 6857664 cyclic: 71328875
CompTox Dashboard (EPA)	linear: DTXSID801315735
InChI InChI=1S/N3/c1-3-2 Key: DUAJIKVIRGATIW-UHFFFAOYSA-N cyclic: InChI=1S/N3/c1-2-3-1 Key: RLXSTAGCZQYHDL-UHFFFAOYSA-N
SMILES linear: [N-]=[N+]=[N] cyclic: N1=N[N]1
Properties
Chemical formula	N3
Molar mass	42.021 g·mol−1
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Infobox references

The linear form of N₃ was discovered in 1956 by B. A. Thrush^[4] by photolysis of hydrogen azide.^[5] As a linear and symmetric molecule, it has D_∞h symmetry, with a nitrogen–nitrogen bond length averaging 1.8115 Å. The first excited electronic state, A²Σ_u, is 4.56 eV above the ground state.^[1]

The cyclic form was identified in 2003 by N. Hansen and A. M. Wodtke using ultraviolet photolysis of chlorine azide. Although the reaction yielded mostly the linear form, about 20% of the molecules were cyclic.^[4][1] The ring has C_2v symmetry^[1]—an isosceles triangle—in contrast to the linear form that has equal N–N bond-lengths.