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Names | |
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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 |
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102490 | |
KEGG | |
PubChem CID | |
RTECS number |
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UNII | |
CompTox Dashboard (EPA) | |
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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: | |
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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). |
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 is a constituent of tobacco smoke. [3]
Carl Graebe and Carl Glaser first isolated the compound from coal tar in 1872. [4]
Several routes exist beginning with extraction from coal tar by distillation. Carbazole concentrates in the anthracene distillate and is 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]
Preparative methods:
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. [9] [10]
Diphenylamine derivatives, being electron rich, are naturally oxidized to carbazoles when heated in air; [11] 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. [12]
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 . [13] Some carbazole alkaloids, especially glybomin B, have been isolated from Glycosmis pentaphylla . [14] [15]
As carbazoles have a relatively rich UV-visible light spectrum, they see application as pigments [4] and photocatalysts. [16] The parent carbazole is used in Hydron Blue production [4] and aminoethylcarbazole is used in pigment violet 23 production. [17]
Carbazoles stabilize triplet emitters in certain light-emitting diodes; [4] in general, they are electron photodonors (hole acceptors). [18]
Carbazole electrochemically oxidizes to a conductive polymer, which has not achieved substantial industrial use. [19] 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.