In chemistry, azide is a

linear Linearity is the property of a mathematical relationship ('' function'') that can be graphically represented as a straight line. Linearity is closely related to '' proportionality''. Examples in physics include rectilinear motion, the linear ...

, polyatomic anion with the formula and structure . It is the

conjugate base A conjugate acid, within the Brønsted–Lowry acid–base theory, is a chemical compound formed when an acid donates a proton () to a base—in other words, it is a base with a hydrogen ion added to it, as in the reverse reaction it loses a ...

of hydrazoic acid .

Organic azide 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 w ...

s are

organic compound In chemistry, organic compounds are generally any chemical compounds that contain carbon- hydrogen or carbon-carbon bonds. Due to carbon's ability to catenate (form chains with other carbon atoms), millions of organic compounds are known. Th ...

s with the formula , containing the azide

functional group In organic chemistry, a functional group is a substituent or moiety in a molecule that causes the molecule's characteristic chemical reactions. The same functional group will undergo the same or similar chemical reactions regardless of the res ...

. The dominant application of azides is as a

propellant A propellant (or propellent) is a mass that is expelled or expanded in such a way as to create a thrust or other motive force in accordance with Newton's third law of motion, and "propel" a vehicle, projectile, or fluid payload. In vehicles, the ...

in air bags.

Preparation

Sodium azide is made industrially by the reaction of

nitrous oxide Nitrous oxide (dinitrogen oxide or dinitrogen monoxide), commonly known as laughing gas, nitrous, or nos, is a chemical compound, an oxide of nitrogen with the formula . At room temperature, it is a colourless non-flammable gas, and has ...

, with

sodium amide Sodium amide, commonly called sodamide (systematic name sodium azanide), is the inorganic compound with the formula . It is a salt composed of the sodium cation and the azanide anion. This solid, which is dangerously reactive toward water, is whit ...

in liquid ammonia as solvent: : Many inorganic azides can be prepared directly or indirectly from sodium azide. For example, lead azide, used in

detonator A detonator, frequently a blasting cap, is a device used to trigger an explosive device. Detonators can be chemically, mechanically, or electrically initiated, the last two being the most common. The commercial use of explosives uses electr ...

s, 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. Some azides are produced by treating the carbonate salts with hydrazoic acid.

Bonding

Azide is

isoelectronic Isoelectronicity is a phenomenon observed when two or more molecules have the same structure (positions and connectivities among atoms) and the same electronic configurations, but differ by what specific elements are at certain locations in th ...

with

carbon dioxide Carbon dioxide ( chemical formula ) is a chemical compound made up of molecules that each have one carbon atom covalently double bonded to two oxygen atoms. It is found in the gas state at room temperature. In the air, carbon dioxide is t ...

cyanate Cyanate is an anion with the structural formula , usually written . It also refers to any salt containing it, such as ammonium cyanate. It is an isomer of the much less stable fulminate anion .William R. Martin and David W. Ball (2019): "Sm ...

, nitronium ion and cyanogen fluoride NCF. Per

valence bond theory In chemistry, valence bond (VB) theory is one of the two basic theories, along with molecular orbital (MO) theory, that were developed to use the methods of quantum mechanics to explain chemical bonding. It focuses on how the atomic orbitals of ...

, azide can be described by several

resonance structure In chemistry, resonance, also called mesomerism, is a way of describing bonding in certain molecules or polyatomic ions by the combination of several contributing structures (or ''forms'', also variously known as ''resonance structures'' or '' ...

s; an important one being

Reactions

Azide salts can decompose with release of nitrogen gas. The decomposition temperatures of the alkali metal azides are: (275 °C), (355 °C), (395 °C), and (390 °C). This method is used to produce ultrapure alkali metals: : Protonation of azide salts gives toxic hydrazoic acid in the presence of strong acids: : Azide as a

ligand In coordination chemistry, a ligand is an ion or molecule ( functional group) that binds to a central metal atom to form a coordination complex. The bonding with the metal generally involves formal donation of one or more of the ligand's ele ...

forms numerous

transition metal azide complex Transition metal azide complexes are coordination complexes containing one or more azide (N3−) ligands. Structure and bonding Azide is a pseudohalide but more nucleophilic than chloride. As a monodentate ligand, azide binds through one of the t ...

es. Some such compound are more shock sensitive. Many inorganic covalent azides (e.g., chlorine, bromine, and iodine azides) have been described. The azide anion behaves as a nucleophile; it undergoes

nucleophilic substitution In chemistry, a nucleophilic substitution is a class of chemical reaction A chemical reaction is a process that leads to the chemical transformation of one set of chemical substances to another. Classically, chemical reactions encompass c ...

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. Azides can be used as precursors of the metal nitrido complexes by being induced to release , generating a metal complex in unusual oxidation states (see '' high-valent iron'').

Disposal

Azides decompose with nitrite compounds such as

sodium nitrite Sodium nitrite is an inorganic compound with the chemical formula NaNO2. It is a white to slightly yellowish crystalline powder that is very soluble in water and is hygroscopic. From an industrial perspective, it is the most important nitrite ...

when acidified. This is a method of destroying residual azides, prior to disposal. In the process, nitrogen, nitrogen oxides, and hydroxides are formed: : :

Applications

About 251 tons of azide-containing compounds are produced annually, the main product being sodium azide.Horst H. Jobelius, Hans-Dieter Scharff "Hydrazoic Acid and Azides" in Ullmann's Encyclopedia of Industrial Chemistry, 2005, Wiley-VCH, Weinheim. Sodium azide is the propellant in automobile

airbag An airbag is a vehicle occupant-restraint system using a bag designed to inflate extremely quickly, then quickly deflate during a Traffic collision, collision. It consists of the airbag cushion, a flexible fabric bag, an inflation module, and a ...

s. It decomposes on heating to give nitrogen gas, which is used to quickly expand the air bag: : Heavy metal azides, such as lead azide, , are shock-sensitive detonators which decompose to the corresponding metal and nitrogen, for example: : Silver azide and

barium azide Barium azide is an inorganic azide with the formula . It is a barium salt of hydrazoic acid. Like most azides, it is explosive. It is less sensitive to mechanical shock than lead azide. Preparation Barium azide may be prepared by reacting sodi ...

are used similarly. Some organic azides are potential rocket propellants, an example being 2-dimethylaminoethylazide (DMAZ) .

Safety

Azides are explosophores and poisons. Sodium azide is as toxic as

sodium cyanide Sodium cyanide is a poisonous compound with the formula Na C N. It is a white, water-soluble solid. Cyanide has a high affinity for metals, which leads to the high toxicity of this salt. Its main application, in gold mining, also exploits its h ...

(with an oral of 27 mg/kg in rats) and can be absorbed through the skin. Heavy metal azides, such as lead azide are

primary Primary or primaries may refer to: Arts, entertainment, and media Music Groups and labels * Primary (band), from Australia * Primary (musician), hip hop musician and record producer from South Korea * Primary Music, Israeli record label Work ...

high explosive An explosive (or explosive material) is a reactive substance that contains a great amount of potential energy that can produce an explosion if released suddenly, usually accompanied by the production of light, heat, sound, and pressure. An e ...

s detonable 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.

References

External links

Synthesis of organic azides
recent methods
Synthesizing, Purifying, and Handling Organic Azides
{{Authority control Azides