Tetrazole

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1H-Tetrazole
Identifiers
3D model (
JSmol
)
ChEBI
ChemSpider
ECHA InfoCard
 100.005.477 Edit this at Wikidata
UNII
  • InChI=1S/CH2N4/c1-2-4-5-3-1/h1H,(H,2,3,4,5) checkY
    Key: KJUGUADJHNHALS-UHFFFAOYSA-N checkY
  • InChI=1/CH2N4/c1-2-4-5-3-1/h1H,(H,2,3,4,5)
    Key: KJUGUADJHNHALS-UHFFFAOYAI
  • InChI=1S/CH2N4/c1-2-4-5-3-1/h1H,(H,2,3,4,5)
    Key: KJUGUADJHNHALS-UHFFFAOYSA-N
  • [nH]1nnnc1
Properties
CH2N4
Molar mass 70.05 g/mol
Density 1.477 g/mL
Melting point 157 to 158 °C (315 to 316 °F; 430 to 431 K)[2]
Boiling point 220 ± 23 °C (428 ± 41 °F; 493 ± 23 K)
Acidity (pKa) 4.90[1]
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
checkY verify (what is checkY☒N ?)

Tetrazoles are a class of synthetic organic heterocyclic compound, consisting of a 5-member ring of four nitrogen atoms and one carbon atom. The name tetrazole also refers to the parent compound with formula CH2N4, of which three isomers can be formulated.

Structure and bonding

Three isomers of the parent tetrazole exist, differing in the position of the double bonds: 1H-, 2H-, and 5H-tetrazole. The 1H- and 2H- isomers are

aromatic
, with 6 π-electrons, while the 5H-isomer is nonaromatic.

Tautomerization of 1H-tetrazole (left) and 2H-tetrazole (middle) in comparison to 5H-tetrazole (right)

Synthesis

1H-Tetrazole was first prepared by the reaction of anhydrous

aminoguanidine.[8][9]

2-Aryl-2H-tetrazoles are synthesized by a [3+2] cycloaddition reaction between an aryl diazonium and trimethylsilyldiazomethane.[10]

Uses

There are several pharmaceutical agents which are tetrazoles, including several cephalosporin-class antibiotics. Tetrazoles can act as bioisosteres for carboxylate groups because they have similar pKa and are deprotonated at physiological pH. Angiotensin II receptor blockers — such as losartan and candesartan, often are tetrazoles. A well-known tetrazole is dimethyl thiazolyl diphenyl tetrazolium bromide (MTT). This tetrazole is used in the

respiratory activity of live cells culture, although it generally kills the cells in the process. Some tetrazoles can also be used in DNA assays.[11] Studies suggest VT-1161 and VT-1129 are a potential potent antifungal drugs as they disturbs fungal enzymatic function but not human enzymes.[12][13]

Some tetrazole

solid rocket propellant formulations.[14][15] These include the azidotetrazolate
salts of nitrogen bases.

Other tetrazoles are used for their explosive or combustive properties, such as tetrazole itself and

airbags. Tetrazole based energetic materials produce high-temperature, non-toxic reaction products such as water and nitrogen gas,[16] and have a high burn rate and relative stability,[17]
all of which are desirable properties. The delocalization energy in tetrazole is 209 kJ/mol.

1H-Tetrazole and 5-(benzylthio)-1H-tetrazole (BTT) are widely used as acidic activators of the coupling reaction in oligonucleotide synthesis.[18]

2-Tetrazoles can undergo controlled

1,3-dipolar cycloaddition reactions.[21]

Scheme 2. Nitrilimine formation
Scheme 2. Nitrilimine formation

Related heterocycles

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

References

  1. doi:10.1039/b203118c
    .
  2. doi:10.1021/jo01151a027
    .
  3. ISSN 0108-2701
    .
  4. ^
    PMID 21322546
    .
  5. J. Chem. Soc.
    Perkin Trans. 2 1983, 379.
  6. ISSN 0002-7863
    .
  7. ISSN 1364-5471
    .
  8. ISSN 0002-7863
    .
  9. ISSN 1521-3773
    .
  10. PMID 27041776
    .
  11. PMID 2922273
    .
  12. PMID 25224009
    .
  13. PMID 26787697
    .
  14. ^ "Greener explosives show promise". Chemistry World. 2 October 2008.
  15. doi:10.1002/zaac.200900521
    .
  16. ISBN 9781118676448. {{cite book}}: |journal= ignored (help
    )
  17. PMID 22214278
    .
  18. doi:10.1016/j.tet.2013.03.001
    .
  19. doi:10.1021/jo01088a034
    .
  20. doi:10.1002/anie.199405271
    .
  21. doi:10.1002/anie.196305651
    .
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