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
CAS Number	86-74-8 Y
3D model (JSmol)	Interactive image
Beilstein Reference	3956
ChEBI	CHEBI:27543 Y
ChEMBL	ChEMBL243580 Y
ChemSpider	6593 Y
DrugBank	DB07301 Y
ECHA InfoCard	100.001.542
EC Number	201-696-0
Gmelin Reference	102490
KEGG	C08060 Y
PubChem CID	6854
RTECS number	FE3150000
UNII	0P2197HHHN Y
CompTox Dashboard (EPA)	DTXSID4020248
InChI InChI=1S/C12H9N/c1-3-7-11-9(5-1)10-6-2-4-8-12(10)13-11/h1-8,13H Y Key: UJOBWOGCFQCDNV-UHFFFAOYSA-N Y 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
SMILES c1ccc2c(c1)c3ccccc3[nH]2
Properties
Chemical formula	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]
Magnetic susceptibility (χ)	−117.4 × 10−6 cm3 mol−1
Hazards
GHS labelling:
Pictograms
Signal word	Warning
Hazard statements	H341, H351, H400, H411, H413
Precautionary statements	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). Y verify (what is YN ?) Infobox references

Carbazole is a constituent of tobacco smoke.^[3]

History

Carl Graebe and Carl Glaser first isolated the compound from coal tar in 1872.^[4]

Production

Few carbazole production methods are economically viable, due to limited demand. During coal tar distillation, carbazole concentrates in the anthracene distillate and must be removed before anthraquinone production; that waste product is the major industrial carbazole source.^[4][5] Polar compounds (e.g., ketones) selectively precipitate it from the anthracene; a more modern technique is simply selective crystallization from molten coal tar at high temperature^[4] or low pressure (70 mmHg).^[6]

A classic laboratory organic synthesis for carbazole is the Borsche–Drechsel cyclization.^[7][8]

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.^[9] 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.^[10]

Bucherer carbazole synthesis

A third method for the synthesis of carbazole is the 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.^[11][12]

Fluorescence of (9H-carbazol-9-yl)(2,4-dichlorophenyl) methanone

Diphenylamine derivatives, being electron rich, naturally oxidize to carbazoles when heated in air.^[13] A similar reaction is the Mallory reaction:

Substituted carbazoles are most easily synthesized with transition metal coupling reactions. For applications that transition-metal impurities in the final product might inhibit, an alternative is nucleophilic aromatic substitution on dibenzothiophene dioxide.^[14]

Natural Occurrence

Main article: Carbazole alkaloids

Carbazoles occur naturally in carbazole alkaloids. Carbazole alkaloids with unsubstituted benzene rings occur rarely. Olivacin has been found in the bark of Aspidosperma olivaceum and ellipticin in Ochrosia elliptica.^[15] Some carbazole alkaloids, especially glybomin B, have been isolated from Glycosmis pentaphylla.^[16]

• 
  Glycozoline
• 
  Olivacine
• 
  Ellipticin
• 
  Glybomine B

Applications

As carbazoles have a relatively rich UV-visible light spectrum, they see application as pigments^[4] and photocatalysts.^[17] The parent carbazole is used in Hydron Blue production^[4] and aminoethylcarbazole is used in pigment violet 23 production.^[18]

Pigment Violet 23 synthesis

Carbazoles stabilize triplet emitters in certain light-emitting diodes;^[4] in general, they are electron photodonors (hole acceptors).^[19]

Carbazole electrochemically oxidizes to a conductive polymer, which has not achieved substantial industrial use.^[20] Polyvinylcarbazole is useful in the electrical and electronic industries, and certain carbazole novolaks are extremely heat resistant.^[4]

In organic chemistry, carbazole proper is also an ingredient for several bioactive molecules. The insecticide Nirosan,^[4] the cocaine overdose antidote Rimcazole, and the veterinary NSAID Carprofen are all made from carbazole. The topoisomerase II inhibitor ellipticine fuses carbazole to a pyridine ring.

See also

• Indole
• Carboline
• Fluorene
• Polychlorinated carbazoles
• Carbazole alkaloids

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. Collin, Gerd; Höke, Hartmut; Talbiersky, Jörg. "Carbazole". Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. doi:10.1002/14356007.a05_059.pub2. ISBN 978-3527306732.{{cite encyclopedia}}: CS1 maint: multiple names: authors list (link)
5. Cofrancesco, A. J., "Anthraquinone", Kirk-Othmer Encyclopedia of Chemical Technology, New York: John Wiley, p. 5, doi:10.1002/0471238961.0114200803150618.a01, ISBN 9780471238966
6. Betts, W. D., "Tar and Pitch", Kirk-Othmer Encyclopedia of Chemical Technology, New York: John Wiley, p. 5, doi:10.1002/0471238961.20011802052020.a01, ISBN 9780471238966
7. 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.
8. E. Drechsel (1888). "Ueber Elektrolyse des Phenols mit Wechselströmen". J. Prakt. Chem. (in German). 38 (1): 65–74. doi:10.1002/prac.18880380105.
9. 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; Collected Volumes, vol. 4, p. 884.
10. Wang, Zerong (2010). "Bucherer Carbazole Synthesis". Comprehensive Organic Name Reactions and Reagents. pp. 549–552. doi:10.1002/9780470638859.conrr120. ISBN 9780470638859.
11. Carl Graebe; Fritz Ullmann (1896). "Ueber eine neue Carbazolsynthese". Justus Liebigs Ann. Chem. (in German). 291 (1): 16–17. doi:10.1002/jlac.18962910104.
12. 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.
13. Vogt, Peter F.; Gerulis, John J. "Amines, Aromatic". Ullmann's Encyclopedia of Industrial Chemistry. Vol. 2. Weinheim: Wiley-VCH. p. 703. doi:10.1002/14356007.a02_037. ISBN 978-3527306732.
14. Bhanuchandra, M.; Yorimitsu Hideki. "Dibenzothiophene 5,5-dioxide". Encyclopedia of Reagents for Organic Synthesis. doi:10.1002/047084289X.rn02046.
15. Eberhard Breitmaier (1997), Alkaloide, Wiesbaden: Springer Fachmedien, p. 49, ISBN 978-3-519-03542-8
17. Rizzo, Carmelo J. (2005). "N-Methylcarbazole". N -Methylcarbazole. Encyclopedia of Reagents for Organic Synthesis. doi:10.1002/047084289X.rn00578. ISBN 0-471-93623-5.
18. U.S. patent 4,345,074
19. Ying Wang, "Photoconductive polymers", Kirk-Othmer Encyclopedia of Chemical Technology, New York: John Wiley, p. 15, doi:10.1002/0471238961.1608152023011407.a01, ISBN 9780471238966
20. Naarmann, Herbert. "Polymers, Electrically conducting". Ullmann's Encyclopedia of Industrial Chemistry. Vol. 29. Weinheim: Wiley-VCH. p. 309. doi:10.1002/14356007.a21_429. ISBN 978-3527306732.

External links

• MSDS