In chemistry, azide is a linear, polyatomic anion with the formula N−3 and structure −N=N+=N−. It is the conjugate base of hydrazoic acid HN3. Organic azides are organic compounds with the formula RN3, containing the azide functional group. The dominant application of azides is as a propellant in air bags.
Sodium azide is an inorganic compound with the formula NaN3. This colorless salt is the gas-forming component in some car airbag systems. It is used for the preparation of other azide compounds. It is an ionic substance, is highly soluble in water, and is very acutely poisonous.
Hydrazoic acid, also known as hydrogen azide, azic acid or azoimide, is a compound with the chemical formula HN3. It is a colorless, volatile, and explosive liquid at room temperature and pressure. It is a compound of nitrogen and hydrogen, and is therefore a pnictogen hydride. The oxidation state of the nitrogen atoms in hydrazoic acid is fractional and is -1/3. It was first isolated in 1890 by Theodor Curtius. The acid has few applications, but its conjugate base, the azide ion, is useful in specialized processes.
Silver azide is the chemical compound with the formula AgN3. It is a silver(I) salt of hydrazoic acid. It forms a colorless crystals. Like most azides, it is a primary explosive.
Copper(II) azide is a medium density explosive with the molecular formula Cu(N3)2.
Trimethylsilyl azide is the organosilicon compound with the formula (CH3)3SiN3. A colorless liquid, it is a reagent in organic chemistry, serving as the equivalent of hydrazoic acid.
In organic chemistry, the Schmidt reaction is an organic reaction in which an azide reacts with a carbonyl derivative, usually an aldehyde, ketone, or carboxylic acid, under acidic conditions to give an amine or amide, with expulsion of nitrogen. It is named after Karl Friedrich Schmidt (1887–1971), who first reported it in 1924 by successfully converting benzophenone and hydrazoic acid to benzanilide. The intramolecular reaction was not reported until 1991 but has become important in the synthesis of natural products. The reaction is effective with carboxylic acids to give amines (above), and with ketones to give amides (below).
Ammonium azide is the chemical compound with the formula [NH4]N3, being the salt of ammonia and hydrazoic acid. Like other inorganic azides, this colourless crystalline salt is a powerful explosive, although it has a remarkably low sensitivity. [NH4]N3 is physiologically active and inhalation of small amounts causes headaches and palpitations. It was first obtained by Theodor Curtius in 1890, along with other azides.
Potassium azide is the inorganic compound having the formula KN3. It is a white, water-soluble salt. It is used as a reagent in the laboratory.
Lithium azide is the lithium salt of hydrazoic acid. It is an unstable and toxic compound that decomposes into lithium and nitrogen when heated.
Barium azide is an inorganic azide with the formula Ba(N3)2. It is a barium salt of hydrazoic acid. Like most azides, it is explosive. It is less sensitive to mechanical shock than lead azide.
Calcium azide is a chemical compound with the formula Ca(N3)2.
Fluorine azide or triazadienyl fluoride is a yellow green gas composed of nitrogen and fluorine with formula FN3. Its properties resemble those of ClN3, BrN3, and IN3. The bond between the fluorine atom and the nitrogen is very weak, leading to this substance being very unstable and prone to explosion. Calculations show the F–N–N angle to be around 102° with a straight line of 3 nitrogen atoms.
Rubidium azide is an inorganic compound with the formula RbN3. It is the rubidium salt of the hydrazoic acid HN3. Like most azides, it is explosive.
Hydrazinium azide or hydrazine azide is a chemical compound with formula H
5N
5 or [N
2H+
5][N−
3]. It is a salt of the hydrazinium cation N
2H+
5 and the azide anion N−
3. It can be seen as a derivative of hydrazine N
2H
4 and hydrazoic acid HN
3. It is an unstable solid.
Zinc azideZn(N3)2 is an inorganic compound composed of zinc cations (Zn2+) and azide anions (N−3). It is a white, explosive solid that can be prepared by the protonolysis of diethylzinc with hydrazoic acid:
Caesium azide or cesium azide is an inorganic compound of caesium and nitrogen. It is a salt of azide with the formula CsN3.
Boron triazide, also known as triazidoborane, is a thermally unstable compound of boron and nitrogen with a nitrogen content of 92.1 %. Formally, it is the triazido derivative of borane and is a covalent inorganic azide. The high-energy compound, which has the propensity to undergo spontaneous explosive decomposition, was first described in 1954 by Egon Wiberg and Horst Michaud of the University of Munich.
An organic azide is an organic compound that contains an azide functional group. Because of the hazards associated with their use, few azides are used commercially although they exhibit interesting reactivity for researchers. Low molecular weight azides are considered especially hazardous and are avoided. In the research laboratory, azides are precursors to amines. They are also popular for their participation in the "click reaction" between an azide and an alkyne and in Staudinger ligation. These two reactions are generally quite reliable, lending themselves to combinatorial chemistry.
Homoleptic azido compounds are chemical compounds in which the only anion or ligand is the azide group, -N3. The breadth of homoleptic azide compounds spans nearly the entire periodic table. With rare exceptions azido compounds are highly shock sensitive and need to be handled with the upmost caution. Binary azide compounds can take on several different structures including discrete compounds, or one- two, and three-dimensional nets, leading some to dub them as "polyazides". Reactivity studies of azide compounds are relatively limited due to how sensitive they can be. The sensitivity of these compounds tends to be correlated with the amount of ionic or covalent character the azide-element bond has, with ionic character being far more stable than covalent character. Therefore, compounds such as silver or sodium azide – which have strong ionic character – tend to possess more synthetic utility than their covalent counterparts. A few other notable exceptions include polymeric networks which possess unique magnetic properties, group 13 azides which unlike most other azides decompose to nitride compounds (important materials for semiconductors), other limited uses as synthetic reagents for the transfer for azide groups, or interest in high energy density materials.
