Carbazole is an

aromatic In chemistry, aromaticity is a chemical property of cyclic ( ring-shaped), ''typically'' planar (flat) molecular structures with pi bonds in resonance (those containing delocalized electrons) that gives increased stability compared to satur ...

heterocyclic A heterocyclic compound or ring structure is a cyclic compound that has atoms of at least two different elements as members of its ring(s). Heterocyclic chemistry is the branch of organic chemistry dealing with the synthesis, properties, and ...

organic compound In chemistry, organic compounds are generally any chemical compounds that contain carbon-hydrogen or carbon-carbon bonds. Due to carbon's ability to catenate (form chains with other carbon atoms), millions of organic compounds are known. T ...

. It has a tricyclic structure, consisting of two six-membered

benzene Benzene is an organic chemical compound with the molecular formula C6H6. The benzene molecule is composed of six carbon atoms joined in a planar ring with one hydrogen atom attached to each. Because it contains only carbon and hydrogen atoms ...

rings fused on either side of a five-membered

nitrogen Nitrogen is the chemical element with the symbol N and atomic number 7. Nitrogen is a nonmetal and the lightest member of group 15 of the periodic table, often called the pnictogens. It is a common element in the universe, estimated at se ...

-containing ring. The compound's structure is based on the

indole Indole is an aromatic heterocyclic organic compound In chemistry, organic compounds are generally any chemical compounds that contain carbon-hydrogen or carbon-carbon bonds. Due to carbon's ability to catenate (form chains with other c ...

structure, but in which a second

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 Tobacco smoke is a sooty aerosol produced by the incomplete combustion of tobacco during the tobacco smoking, smoking of cigarettes and other tobacco products. Temperatures in burning cigarettes range from about 400 °C between puffs to abo ...

Synthesis

A classic laboratory

organic synthesis Organic synthesis is a special branch of chemical synthesis and is concerned with the intentional construction of organic compounds. Organic molecules are often more complex than inorganic compounds, and their synthesis has developed into one o ...

for carbazole is the

Borsche–Drechsel cyclization The Borsche–Drechsel cyclization is a chemical reaction used to synthesize tetrahydrocarbazoles by the acid-catalyzed cyclization of cyclohexanone arylhydrazones. The reaction was first described by Edmund Drechsel in 1888 and by Walter Borsche i ...

In the first step,

phenylhydrazine Phenylhydrazine is the chemical compound with the formula . It is often abbreviated as . It is also found in edible mushrooms. Properties Phenylhydrazine forms monoclinic prisms that melt to an oil around room temperature which may turn yellow ...

is condensed with

cyclohexanone Cyclohexanone is the organic compound with the formula (CH2)5CO. The molecule consists of six-carbon cyclic molecule with a ketone functional group. This colorless oily liquid has an odor reminiscent of acetone. Over time, samples of cyclohexan ...

to the corresponding

imine In organic chemistry, an imine ( or ) is a functional group or organic compound containing a carbon–nitrogen double bond (). The nitrogen atom can be attached to a hydrogen or an organic group (R). The carbon atom has two additional single bo ...

. The second step is a

hydrochloric acid Hydrochloric acid, also known as muriatic acid, is an aqueous solution of hydrogen chloride. It is a colorless solution with a distinctive pungent smell. It is classified as a strong acid Acid strength is the tendency of an acid, symbol ...

-catalyzed

rearrangement reaction In organic chemistry, a rearrangement reaction is a broad class of organic reactions where the carbon skeleton of a molecule is rearranged to give a structural isomer of the original molecule. Often a substituent moves from one atom to another ...

and

ring-closing reaction A cyclic compound (or ring compound) is a term for a compound in the field of chemistry in which one or more series of atoms in the compound is connected to form a ring. Rings may vary in size from three to many atoms, and include examples where ...

to tetrahydrocarbazole. In one modification, both steps are rolled into one by carrying out the reaction in

acetic acid Acetic acid , systematically named ethanoic acid , is an acidic, colourless liquid and organic compound with the chemical formula (also written as , , or ). Vinegar is at least 4% acetic acid by volume, making acetic acid the main component ...

. In the third step, this compound is oxidized by

red lead Red is the color at the long wavelength end of the visible spectrum of light, next to orange and opposite violet. It has a dominant wavelength of approximately 625–740 nanometres. It is a primary color in the RGB color model and a secondar ...

to carbazole itself. Another classic is the

Bucherer carbazole synthesis The Bucherer carbazole synthesis is a chemical reaction used to synthesize carbazoles from naphthols and aryl hydrazines using sodium bisulfite Sodium bisulfite (or sodium bisulphite, sodium hydrogen sulfite) is a chemical mixture with the app ...

, which uses a naphthol and an aryl hydrazine. Bucherer_Carbazole_Synthesis_Scheme

A third method for the synthesis of carbazole is the Graebe–Ullmann reaction. Reacción de Graebe-Ullman

In the first step, an ''N''-phenyl-1,2-diaminobenzene (''N''-phenyl- ''o''-phenylenediamine) is converted into a

diazonium Diazonium compounds or diazonium salts are a group of organic compounds sharing a common functional group where R can be any organic group, such as an alkyl or an aryl, and X is an inorganic or organic anion, such as a halide. General properti ...

salt Salt is a mineral composed primarily of sodium chloride (NaCl), a chemical compound belonging to the larger class of salts; salt in the form of a natural crystalline mineral is known as rock salt or halite. Salt is present in vast quantitie ...

which instantaneously forms a 1,2,3-triazole. The triazole is unstable and at elevated temperatures, nitrogen is released and the carbazole is formed.

Applications

Aminoethylcarbazole is used in the production of

pigment violet 23 Pigment violet 23 is an organic compound that is a commercial pigment. It is member of the di oxazine family of heterocyclic compounds, but derived from carbazoles. It is prepared by condensation of chloranil and 3-amino-''N''-ethylcarbazole. It ...

Rimcazole Rimcazole is an antagonist of the sigma receptor as well as a dopamine reuptake inhibitor. Sigma receptors are thought to be involved in the drug psychosis that can be induced by some drugs such as phencyclidine and cocaine, and rimcazole was ori ...

is also made from carbazole proper. *

Carprofen Carprofen is a non-steroidal anti-inflammatory drug (NSAID) of the propionic acid class that was previously for use in humans and animals, but is now only available to veterinarians for prescribing as a supportive treatment for various conditions ...

is another use.

Related aromatic compounds

Indoline Indoline is an aromatic heterocyclic organic compound with the chemical formula C8H9N. It has a bicyclic structure, consisting of a six-membered benzene ring fused to a five-membered nitrogen-containing ring. The compound is based on the indole st ...

Indole Indole is an aromatic heterocyclic organic compound with the formula C8 H7 N. It has a bicyclic structure, consisting of a six-membered benzene ring fused to a five-membered pyrrole ring. Indole is widely distributed in the natural environmen ...

Carboline β-Carboline (9''H''- pyrido ,4-''b'' ndole) represents the basic chemical structure for more than one hundred alkaloids and synthetic compounds. The effects of these substances depend on their respective substituent. Natural β-carbolines prim ...

* Fluorene *

Pyrrole Pyrrole is a heterocyclic aromatic organic compound, a five-membered ring with the formula C4 H4 NH. It is a colorless volatile liquid that darkens readily upon exposure to air. Substituted derivatives are also called pyrroles, e.g., ''N''-meth ...

* ''N''-Vinylcarbazole

References

External links

MSDS
{{Authority control Carbazoles IARC Group 2B carcinogens