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chemistry Chemistry is the scientific study of the properties and behavior of matter. It is a natural science that covers the elements that make up matter to the compounds made of atoms, molecules and ions: their composition, structure, proper ...
, 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 In science, a formula is a concise way of expressing information symbolically, as in a mathematical formula or a ''chemical formula''. The informal use of the term ''formula'' in science refers to the general construct of a relationship betwe ...
and
structure A structure is an arrangement and organization of interrelated elements in a material object or system, or the object or system so organized. Material structures include man-made objects such as buildings and machines and natural objects such a ...
. 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 azides 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 r ...
. 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 ha ...
, with sodium amide in liquid ammonia as solvent: : Many inorganic azides can be prepared directly or indirectly from sodium azide. For example,
lead azide Lead(II) azide is an inorganic compound. More so than other azides, is explosive. It is used in detonators to initiate secondary explosives. In a commercially usable form, it is a white to buff powder. Preparation and handling Lead(II) azide i ...
, used in detonators, 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 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 ,
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 ha ...
, nitronium ion and cyanogen fluoride NCF. Per valence bond theory, 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 elect ...
forms numerous transition metal azide complexes. 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 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 High-valent iron commonly denotes compounds and intermediates in which iron is found in a formal oxidation state > 3 that show a number of bonds > 6 with a coordination number ≤ 6. The term is rather uncommon for hepta-coordinate compounds of ...
'').


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 airbags. It decomposes on heating to give nitrogen gas, which is used to quickly expand the air bag: : Heavy metal azides, such as
lead azide Lead(II) azide is an inorganic compound. More so than other azides, is explosive. It is used in detonators to initiate secondary explosives. In a commercially usable form, it is a white to buff powder. Preparation and handling Lead(II) azide i ...
, , 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
explosophore Explosophores are functional groups in organic chemistry that give organic compounds explosive properties. History The term was first coined by Russian chemist V. Pletz in 1935 and originally mistranslated in some articles as plosophore. Also o ...
s and poisons. Sodium azide is as toxic as sodium cyanide (with an oral of 27 mg/kg in rats) and can be absorbed through the skin. Heavy metal azides, such as
lead azide Lead(II) azide is an inorganic compound. More so than other azides, is explosive. It is used in detonators to initiate secondary explosives. In a commercially usable form, it is a white to buff powder. Preparation and handling Lead(II) azide i ...
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 Works ...
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 ...
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 evaporator A rotary evaporator (rotovap) is a device used in chemical laboratories for the efficient and gentle removal of solvents from samples by evaporation. When referenced in the chemistry research literature, description of the use of this technique and ...
s, freezedrying equipment, cooling traps, water baths, waste pipes), and thus lead to violent explosions.


See also

* Pentazenium *
Pentazolate In chemistry, a pentazolate is a compound that contains a ''cyclo''-N5− ion, the anion of pentazole. In 2017, researchers prepared the first salt (N5)6(H3O)3(NH4)4Cl containing pentazolate anion starting a substituted phenylpentazole, ''m''-CPB ...
(''cyclo''-N5)


References


External links


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