Carbazole

Carbazole is an aromatic heterocyclic organic compound. It has a tricyclic structure, consisting of two six-membered benzene rings fused on either side of a five-membered nitrogen-containing ring. The compound's structure is based on the indole structure, but in which a second benzene ring is fused onto the five-membered ring at the 2–3 position of indole (equivalent to the 9a–4a double bond in carbazole, respectively).

Carbazole
Names
Preferred IUPAC name
9H-Carbazole[1]
Other names
9-azafluorene
dibenzopyrrole
diphenylenimine
diphenyleneimide
USAF EK-600
Identifiers
3D model (JSmol)
3956
ChEBI
ChEMBL
ChemSpider
DrugBank
ECHA InfoCard 100.001.542
EC Number
  • 201-696-0
102490
KEGG
RTECS number
  • FE3150000
UNII
  • InChI=1S/C12H9N/c1-3-7-11-9(5-1)10-6-2-4-8-12(10)13-11/h1-8,13H checkY
    Key: UJOBWOGCFQCDNV-UHFFFAOYSA-N checkY
  • InChI=1/C12H9N/c1-3-7-11-9(5-1)10-6-2-4-8-12(10)13-11/h1-8,13H
    Key: UJOBWOGCFQCDNV-UHFFFAOYAV
  • c1ccc2c(c1)c3ccccc3[nH]2
Properties
C12H9N
Molar mass 167.211 g·mol−1
Density 1.301 g cm−3
Melting point 246.3 °C (475.3 °F; 519.5 K)[2]
Boiling point 354.69 °C (670.44 °F; 627.84 K)[2]
−117.4 × 10−6 cm3 mol−1
Hazards
GHS labelling:
GHS08: Health hazardGHS09: Environmental hazard
Warning
H341, H351, H400, H411, H413
P201, P202, P273, P281, P308+P313, P391, P405, P501
Flash point 220 °C (428 °F; 493 K)[2]
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 ?)
Infobox references

Carbazole is a constituent of tobacco smoke.[3]

Synthesis

A classic laboratory organic synthesis for carbazole is the Borsche–Drechsel cyclization.[4][5]

Borsche–Drechsel synthesis
Borsche–Drechsel synthesis

In the first step, phenylhydrazine is condensed with cyclohexanone to the corresponding imine. The second step is a hydrochloric acid-catalyzed rearrangement reaction and ring-closing reaction to tetrahydrocarbazole. In one modification, both steps are rolled into one by carrying out the reaction in acetic acid.[6] In the third step, this compound is oxidized by red lead to carbazole itself.

Another classic is the Bucherer carbazole synthesis, which uses a naphthol and an aryl hydrazine.[7]

Bucherer carbazole synthesis
Bucherer carbazole synthesis

A third method for the synthesis of carbazole is the Graebe–Ullmann reaction.

Graebe–Ullmann reaction
Graebe–Ullmann reaction

In the first step, an N-phenyl-1,2-diaminobenzene (N-phenyl-o-phenylenediamine) is converted into a diazonium salt which instantaneously forms a 1,2,3-triazole. The triazole is unstable and at elevated temperatures, nitrogen is released and the carbazole is formed.[8][9]

Applications

Aminoethylcarbazole is used in the production of pigment violet 23.

CI Pigment Violet 23 synthesis: U.S. Patent 4,345,074

References
  1. International Union of Pure and Applied Chemistry (2014). Nomenclature of Organic Chemistry: IUPAC Recommendations and Preferred Names 2013. The Royal Society of Chemistry. p. 212. doi:10.1039/9781849733069. ISBN 978-0-85404-182-4.
  2. Lide, David R. (2007). CRC Handbook of Chemistry and Physics, 88th Edition. CRC Press. pp. 3–86. ISBN 978-0-8493-0488-0.
  3. Talhout, Reinskje; Schulz, Thomas; Florek, Ewa; Van Benthem, Jan; Wester, Piet; Opperhuizen, Antoon (2011). "Hazardous Compounds in Tobacco Smoke". Int. J. Environ. Res. Public Health. 8 (12): 613–628. doi:10.3390/ijerph8020613. PMC 3084482. PMID 21556207.
  4. W. Borsche (1908). "Ueber Tetra- und Hexahydrocarbazolverbindungen und eine neue Carbazolsynthese. (Mitbearbeitet von. A. Witte und W. Bothe.)". Justus Liebigs Ann. Chem. (in German). 359 (1–2): 49–80. doi:10.1002/jlac.19083590103.
  5. E. Drechsel (1888). "Ueber Elektrolyse des Phenols mit Wechselströmen". J. Prakt. Chem. (in German). 38 (1): 65–74. doi:10.1002/prac.18880380105.
  6. Rogers, Crosby U.; Corson, B. B. (1950). "1,2,3,4-Tetrahydrocarbazole (Carbazole, 1,2,3,4-tetrahydro-)". Organic Syntheses. 30: 90. doi:10.15227/orgsyn.030.0090.; Collective Volume, vol. 4, p. 884
  7. Wang, Zerong (2010). "Bucherer Carbazole Synthesis". Comprehensive Organic Name Reactions and Reagents. doi:10.1002/9780470638859.conrr120. ISBN 9780470638859.
  8. Carl Graebe; Fritz Ullmann (1896). "Ueber eine neue Carbazolsynthese". Justus Liebigs Ann. Chem. (in German). 291 (1): 16–17. doi:10.1002/jlac.18962910104.
  9. O. Bremer (1934). "Über die Bedeutung der Graebe-Ullmannschen Carbazolsynthese und deren Übertragung auf N-substituierte Pyridino-triazole". Justus Liebigs Ann. Chem. (in German). 514 (1): 279–291. doi:10.1002/jlac.19345140116.
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