Tetrazole

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Tetrazole
Tetrazole numbering.png Tetrazole3d.png
Identifiers
CAS number 288-94-8 YesY
PubChem 67519
ChemSpider 60842 YesY
ChEBI CHEBI:33193 YesY
Jmol-3D images Image 1
Properties
Molecular formula CH2N4
Molar mass 70.05 g/mol
Density 1.477 g/mL
Melting point 157-158 °C [1]
Boiling point 220±23 °C
Acidity (pKa) 4.90 [2]
Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
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Infobox references

Tetrazoles are a class of synthetic organic heterocyclic compound, consisting of a 5-member ring of four nitrogen and one carbon atom (plus hydrogens). The simplest is tetrazole itself, CN4H2. They are unknown in nature.

Synthesis[edit]

Tetrazole was first prepared by the reaction of anhydrous hydrazoic acid and hydrogen cyanide under pressure. Treatment of organic nitriles with sodium azide in the presence of iodine or silica-supported sodium hydrogen sulfate as a heterogeneous catalyst enables an advantageous synthesis of 5-substituted 1H-tetrazoles.[3]

Uses[edit]

There are several pharmaceutical agents which are tetrazoles. The tetrazole ring can act as a bioisostere for the carboxylate group. Angiotensin II receptor blockers, in particular, such as losartan and candesartan, often contain tetrazoles.

A well-known tetrazole is dimethyl thiazolyl diphenyl tetrazolium salt (MTT). This tetrazole is used in the MTT assay to quantify the respiratory activity of live cells in cell culture, although it generally kills the cells in the process. Tetrazole's derivatives can also be used in DNA synthesis.[4]

Some tetrazole derivatives with high energy have been investigated as high performance explosives as a replacement for TNT and also for use in high performance solid rocket propellant formulations.[5][6]

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 generators in automobile airbags. Tetrazole based energetic materials produce high-temperature, non-toxic reaction products such as water and nitrogen gas,[7] and have a high burn rate and relative stability,[8] all of which are desirable properties. The delocalization energy in tetrazole is 209 kJ/mol.

Related heterocycles[edit]

  • Triazoles, analogs with three nitrogen atoms
  • Pentazole, the analog with five nitrogen atoms (strictly speaking, an inorganic homocycle, not a heterocycle)

References[edit]

  1. ^ Mihina, Joseph S.; Herbst, Robert M. (1950). "The Reaction of Nitriles with Hydrazoic Acid: Synthesis of Monosubstituted Tetrazoles". J. Org. Chem. 15 (5): 1082–1092. doi:10.1021/jo01151a027. 
  2. ^ Satchell, Jacqueline F.; Smith, Brian J. (2002). "Calculation of aqueous dissociation constants of 1,2,4-triazole and tetrazole: A comparison of solvation models". Phys. Chem. Chem. Phys. 4 (18): 4314–4318. Bibcode:2002PCCP....4.4314S. doi:10.1039/b203118c. 
  3. ^ B.Das, C. R. Reddy, D. N. Kumar, M. Krishnaiah, R. Narender (2010). Synlett: 391–394. 
  4. ^ S Berner, K Mühlegger, and H Seliger (Feb 11, 1989). "Studies on the role of tetrazole in the activation of phosphoramidites". Nucleic Acids Res 17 (3): 853–864. PMC 331708. 
  5. ^ "Greener explosives show promise". Chemistry World. 2 October 2008. 
  6. ^ Niko Fischer, Konstantin Karaghiosoff, Thomas M. Klapötke and Jörg Stierstorfer (April 2010). "New Energetic Materials featuring Tetrazoles and Nitramines – Synthesis, Characterization and Properties". Zeitschrift für anorganische und allgemeine Chemie 636 (5): 735–749. doi:10.1002/zaac.200900521. 
  7. ^ Tore Brinck, Thomas M. Klapötke and Jörg Stierstorfer. "Energetic Tetrazole N-oxides". Green Energetic Materials. doi:10.1002/9781118676448.ch06. 
  8. ^ Nicholas Piekiel and Michael R. Zachariah (2012). "Decomposition of Aminotetrazole Based Energetic Materials under High Heating Rate Conditions". J. Phys. Chem. A 116 (6): 1519–1526. doi:10.1021/jp203957t.