Tetrazoles are a class of synthetic
Chemical synthesis
In chemistry, chemical synthesis is purposeful execution of chemical reactions to get a product, or several products. This happens by physical and chemical manipulations usually involving one or more reactions...

 organic heterocyclic
Heterocyclic compound
A heterocyclic compound is a cyclic compound which has atoms of at least two different elements as members of its ring. The counterparts of heterocyclic compounds are homocyclic compounds, the rings of which are made of a single element....

Organic compound
An organic compound is any member of a large class of gaseous, liquid, or solid chemical compounds whose molecules contain carbon. For historical reasons discussed below, a few types of carbon-containing compounds such as carbides, carbonates, simple oxides of carbon, and cyanides, as well as the...

, consisting of a 5-member ring of four nitrogen
Nitrogen is a chemical element that has the symbol N, atomic number of 7 and atomic mass 14.00674 u. Elemental nitrogen is a colorless, odorless, tasteless, and mostly inert diatomic gas at standard conditions, constituting 78.08% by volume of Earth's atmosphere...

 and one carbon
Carbon is the chemical element with symbol C and atomic number 6. As a member of group 14 on the periodic table, it is nonmetallic and tetravalent—making four electrons available to form covalent chemical bonds...

 atom (plus hydrogens). The simplest is tetrazole itself, CN4H2. They are unknown in nature. There are several pharmaceutical agents which are tetrazoles, but they are generally undesirable due to safety concerns for process-scale synthesis; tetrazoles are usually explosive. However, tetrazoles can act as a bioisostere
In medicinal chemistry, bioisosteres are substituents or groups with similar physical or chemical properties which produce broadly similar biological properties to a chemical compound. In drug design, the purpose of exchanging one bioisostere for another is to enhance the desired biological or...

 for the carboxylate group
Carboxylic acid
Carboxylic acids are organic acids characterized by the presence of at least one carboxyl group. The general formula of a carboxylic acid is R-COOH, where R is some monovalent functional group...

, increasing their utility. Angiotensin
Angiotensin, a peptide hormone, causes blood vessels to constrict, and drives blood pressure up. It is part of the renin-angiotensin system, which is a major target for drugs that lower blood pressure. Angiotensin also stimulates the release of aldosterone, another hormone, from the adrenal cortex...

 II receptor blockers, in particular, often contain tetrazoles, such as losartan
Losartan is an angiotensin II receptor antagonist drug used mainly to treat high blood pressure . Losartan was the first angiotensin II receptor antagonist to be marketed. Losartan potassium is marketed by Merck & Co. Inc. under the trade name Cozaar...

 and candesartan
Candesartan is an angiotensin II receptor antagonist used mainly for the treatment of hypertension. The prodrug candesartan cilexetil is marketed by AstraZeneca and Takeda Pharmaceuticals, commonly under the trade names Blopress, Atacand, Amias, and Ratacand.-Clinical use:As all angiotensin II...

. A well-known tetrazole is MTT, which is a dimethyl thiazolyl diphenyl tetrazolium salt. This tetrazole is used in the MTT assay
MTT assay
The MTT assay and the MTS assay are colorimetric assays for measuring the activity of enzymes that reduce MTT or close dyes to formazan dyes, giving a purple color. A main application allows to assess the viability and the proliferation of cells...

 to quantify the respiratory activity of live cells in cell culture
Cell culture
Cell culture is the complex process by which cells are grown under controlled conditions. In practice, the term "cell culture" has come to refer to the culturing of cells derived from singlecellular eukaryotes, especially animal cells. However, there are also cultures of plants, fungi and microbes,...

, although it generally kills the cells in the process.

Other tetrazoles are used for their explosive or combustive properties, such as tetrazole itself and 5-aminotetrazole, which are sometimes used as a component of gas generator
Gas generator
A gas generator usually refers to a device, often similar to a solid rocket or a liquid rocket that burns to produce large volumes of relatively cool gas, instead of maximizing the temperature and specific impulse. The low temperature allows the gas to be put to use more easily in many...

s in automobile
An automobile, autocar, motor car or car is a wheeled motor vehicle used for transporting passengers, which also carries its own engine or motor...

 airbags. They produce high-temperature, non-toxic reaction products, and have a high burn rate and (relative) stability, all of which are desirable properties.

Tetrazole was first prepared by the reaction of anhydrous hydrazoic acid
Hydrazoic acid
Hydrazoic acid, also known as hydrogen azide or azoimide, is a colorless, volatile, and extremely explosive liquid at room temperature and pressure. It is a compound of nitrogen and hydrogen, having chemical formula HN3. It was first isolated in 1890 by Theodor Curtius...

 and hydrogen cyanide under pressure.

Related heterocycles

  • Triazole
    Triazole refers to either one of a pair of isomeric chemical compounds with molecular formula C2H3N3, having a five-membered ring of two carbon atoms and three nitrogen atoms.The two isomers are:*1,2,3-Triazole 100px*1,2,4-Triazole 100px...

    s, analogs with three nitrogen atoms
  • Pentazole
    Pentazole is an aromatic chemical molecule consisting of a five-membered ring with all nitrogen atoms, one of which is bonded to a hydrogen atom. It has a molecular formula of HN5. Its SMILES structure is...

    , the analog with five nitrogen atoms (strictly speaking, an inorganic homocycle, not a heterocycle)
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