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Heterocyclic compound

 

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Heterocyclic compound



 
 
Heterocyclic compounds are organic compound
Organic compound

An organic compound is any member of a large class of chemical compounds whose molecules contain carbon. For historical reasons discussed below, a few types of compounds such as carbonates, simple oxides of carbon and cyanides, as well as the allotropes of carbon, are considered Inorganic compound....
s containing at least one atom of carbon
Carbon

Carbon is a chemical element with chemical symbol C and atomic number 6. As a member of group 14 on the periodic table, it is nonmetallic and tetravalence?making four electrons available to form covalent bond chemical bonds....
, and at least one element other than carbon, such as sulfur
Sulfur

Sulfur or sulphur is the chemical element that has the atomic number 16. It is denoted with the symbol S. It is an abundant Valence non-metal....
, oxygen
Oxygen

Oxygen no O2 produced; 2) O2 produced, but absorbed in oceans & seabed rock; 3) O2 starts to gas out of the oceans, but is absorbed by land surfaces and formation of ozone layer; 4-5) O2 sinks filled and the gas accumulates]]...
 or nitrogen
Nitrogen

Nitrogen is a chemical element that has the symbol N and atomic number 7 and atomic mass 14.00674?. Elemental nitrogen is a colorless, odorless, tasteless and mostly inert diatomic gas at standard conditions, constituting 78% by volume of Earth's atmosphere....
 within a ring structure. These structures may comprise either simple aromatic ring
Simple aromatic ring

Simple aromatic rings, also known as simple arenes or simple aromatics, are aromatic organic compounds that consist only of a conjugated system planar ring system with delocalized_electron pi electron clouds....
s or non-aromatic rings. Some examples are pyridine
Pyridine

Pyridine is a simple and important heterocyclic aromatic organic compound with the formula CarbonHydrogenNitrogen. This colorless liquid with a distinctive fish-like odor is structurally related to benzene, wherein one CH group in the six-membered ring is replaced by a nitrogen atom....
 (C5H5N), pyrimidine
Pyrimidine

Pyrimidine is a heterocyclic aromatic organic compound similar to benzene and pyridine, containing two nitrogen atoms at positions 1 and 3 of the six-member ring....
 (C4H4N2) and dioxane (C4H8O2).

Note that compounds such as cyclopropane
Cyclopropane

Cyclopropane is a cycloalkane molecule with the molecular formula C3H6, consisting of three carbon atoms linked to each other to form a ring, with each carbon atom bearing two hydrogen atoms....
, an anaesthetic with explosive properties, and cyclohexane
Cyclohexane

Cyclohexane is a cycloalkane with the molecular formula Carbon6Hydrogen12. Cyclohexane is used as a nonpolar solvent for the chemical industry, and also as a raw material for the industrial production of adipic acid and caprolactam, both of which are intermediates used in the production of nylon....
, a solvent, are not heterocyclic; they are merely cycloalkanes.






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Heterocyclic compounds are organic compound
Organic compound

An organic compound is any member of a large class of chemical compounds whose molecules contain carbon. For historical reasons discussed below, a few types of compounds such as carbonates, simple oxides of carbon and cyanides, as well as the allotropes of carbon, are considered Inorganic compound....
s containing at least one atom of carbon
Carbon

Carbon is a chemical element with chemical symbol C and atomic number 6. As a member of group 14 on the periodic table, it is nonmetallic and tetravalence?making four electrons available to form covalent bond chemical bonds....
, and at least one element other than carbon, such as sulfur
Sulfur

Sulfur or sulphur is the chemical element that has the atomic number 16. It is denoted with the symbol S. It is an abundant Valence non-metal....
, oxygen
Oxygen

Oxygen no O2 produced; 2) O2 produced, but absorbed in oceans & seabed rock; 3) O2 starts to gas out of the oceans, but is absorbed by land surfaces and formation of ozone layer; 4-5) O2 sinks filled and the gas accumulates]]...
 or nitrogen
Nitrogen

Nitrogen is a chemical element that has the symbol N and atomic number 7 and atomic mass 14.00674?. Elemental nitrogen is a colorless, odorless, tasteless and mostly inert diatomic gas at standard conditions, constituting 78% by volume of Earth's atmosphere....
 within a ring structure. These structures may comprise either simple aromatic ring
Simple aromatic ring

Simple aromatic rings, also known as simple arenes or simple aromatics, are aromatic organic compounds that consist only of a conjugated system planar ring system with delocalized_electron pi electron clouds....
s or non-aromatic rings. Some examples are pyridine
Pyridine

Pyridine is a simple and important heterocyclic aromatic organic compound with the formula CarbonHydrogenNitrogen. This colorless liquid with a distinctive fish-like odor is structurally related to benzene, wherein one CH group in the six-membered ring is replaced by a nitrogen atom....
 (C5H5N), pyrimidine
Pyrimidine

Pyrimidine is a heterocyclic aromatic organic compound similar to benzene and pyridine, containing two nitrogen atoms at positions 1 and 3 of the six-member ring....
 (C4H4N2) and dioxane (C4H8O2).

Note that compounds such as cyclopropane
Cyclopropane

Cyclopropane is a cycloalkane molecule with the molecular formula C3H6, consisting of three carbon atoms linked to each other to form a ring, with each carbon atom bearing two hydrogen atoms....
, an anaesthetic with explosive properties, and cyclohexane
Cyclohexane

Cyclohexane is a cycloalkane with the molecular formula Carbon6Hydrogen12. Cyclohexane is used as a nonpolar solvent for the chemical industry, and also as a raw material for the industrial production of adipic acid and caprolactam, both of which are intermediates used in the production of nylon....
, a solvent, are not heterocyclic; they are merely cycloalkanes. The stem '-cyclic' implies a ring structure, whereas 'hetero' refers to an atom other than carbon, as above. Many heterocyclic compounds, including some amine
Amine

Amines are organic compounds and functional groups that contain a base nitrogen atom with a lone pair. Amines are derivative s of ammonia, wherein one or more hydrogen atoms are replaced by organic substituents such as alkyl and aryl groups....
s, are carcinogenic.

Heterocyclic chemistry is the chemistry branch dealing exclusively with synthesis, properties, and applications of heterocycles. IUPAC name is Hantzsch-Widman nomenclature.

3-Membered rings


Heterocycles with three atoms in the ring are more reactive because of ring strain
Ring strain

Ring strain is an organic chemistry term that describes the destabilization of a cyclic molecule?such as a cycloalkane?due to the non-favorable high energy Molecular geometry of its atoms....
. Those containing one heteroatom are, in general, stable. Those with two heteroatoms are more likely to occur as reactive intermediates. Common 3-membered heterocycles are:

Heteroatom Saturated Unsaturated
Nitrogen Aziridine
Aziridine

Aziridines are a group of organic compounds sharing the aziridine functional group which is a three membered heterocycle with one amine group and two methylene groups....
Azirine
Oxygen Ethylene oxide
Ethylene oxide

Ethylene oxide is the organic compound with the chemical formula C2H4O. This colorless flammable gas with a faintly sweet odor is the simplest epoxide, a three-membered ring consisting of two carbon and one oxygen atom....
 (epoxide
Epoxide

An epoxide is a cyclic ether with only three ring atoms. This ring approximately is an equilateral triangle which makes it highly ring strain....
s, oxiranes)
Oxirene
Sulfur Thiirane
Thiirane

Thiirane, more commonly known as ethylene sulfide, is the cyclic chemical compound with the formula C2H4S. It is the smallest sulfur-containing heterocycle....
 (episulfide
Episulfide

Episulfides are a class of organic compounds that contain a Saturation heterocycle consisting of two carbon atoms and one sulfur atom. It is the sulfur analogue of an epoxide or aziridine. The parent episulfide is thiirane....
s)
 


Those with two heteroatoms include:

Heteroatom Saturated Unsaturated
Oxygen Dioxirane
Dioxirane

A dioxirane is a molecule containing a three-membered ring composed of one carbon and two oxygens. Somewhat unstable, they are used in organic synthesis as oxidizing reagents....
 


4-Membered rings


Compounds with one heteroatom:

Heteroatom Saturated Unsaturated
Nitrogen Azetidine
Azetidine

Azetidine is a heterocyclic organic compound. It belongs to the class of four membered rings and it contains a nitrogen atom....
 
Oxygen Oxetane
Oxetane

Oxetane is the heterocycle organic compound having a four-membered ring with three carbon atoms and one oxygen atom with the molecular formula C3H6O....
 
Sulfur Thietane 


Compounds with two heteroatoms:

Heteroatom Saturated Unsaturated
Oxygen Dioxetane
Dioxetane

Dioxetanes are heterocyclic compound organic compounds which consist of a four-membered ring that contains two oxygen atoms and two carbon atoms....
 
Sulfur Dithietane
Dithietane

Dithietanes are saturated heterocyclic compounds that contain two sulfur atoms and two sp3-hybridized carbon centers. Two isomers are possible for this class of organosulfur compounds, 1,2-dithietanes, where the sulfur atoms are adjacent, and 1,3-dithietanes, where the sulfur atoms are not adjacent....
Dithiete
Dithiete

Dithietes are unsaturated heterocyclic compounds that contain two sulfur atoms and two sp2-hybridized carbon centers. Having 6-pi electrons, dithietes are aromaticity....


5-Membered rings


With heterocycles containing five atoms, the unsaturated compounds
Unsaturated compound

In organic chemistry, an unsaturated compound is a chemical compound that contains carbon-carbon double bonds or triple bonds such as in alkenes or alkynes....
 are frequently more stable because of aromaticity
Aromaticity

Aromaticity is a chemical property in which a conjugated system ring of unsaturated bonds, lone pairs, or empty orbitals exhibit a stabilization stronger than would be expected by the stabilization of conjugation alone....
.

Five-membered rings with a single heteroatom:

Heteroatom Saturated Unsaturated
Nitrogen Tetrahydropyrrole (azolidine, pyrrolidine
Pyrrolidine

Pyrrolidine, also known as tetrahydropyrrole, is an organic compound with the molecular formula C4H9N. It is a cyclic amine with a five-membered ring containing four carbon atoms and one nitrogen atom....
)
Dihydropyrrole (pyrroline
Pyrroline

Pyrrolines, also known under the name dihydropyrroles, are three different heterocyclic compound organic chemistry chemical compounds which differ in the position of the double bond....
), Pyrrole
Pyrrole

Pyrrole, or pyrrol, is a heterocyclic aromatic organic compound, a five-membered ring with the chemical formula carbon4hydrogen4nitrogenH....
Oxygen Tetrahydrofuran
Tetrahydrofuran

Tetrahydrofuran is a colorless, water-miscible organic liquid with low-viscosity at "room" temperature and pressure . It is a Heterocyclic compound compound with a chemical formula C4H8O, and is the fully Hydrogenation analog of the aromatic organic compound furan....
 (oxolane)
Dihydrofuran, Furan
Furan

Furan, also known as furane and furfuran, is a Heterocyclic compound organic compound. It is typically derived by the thermal decomposition of pentose-containing materials, cellulosic solids especially pine-wood....
Sulfur Tetrahydrothiophene
Tetrahydrothiophene

Tetrahydrothiophene is a heterocyclic organic compound consisting of a five-membered ring containing four carbon atoms and a sulfur atom. It is the saturation analog of thiophene....
 (thiolane)
Dihydrothiophene, Thiophene
Thiophene

Thiophene is the heterocyclic compound with the formula C4H4S. Consisting of a flat five-membered ring, it is aromaticity as indicated by its extensive substitution reactions....
Arsenic  Arsole
Arsole

Arsole, rarely called arsenole, is a cyclic organoarsenic chemical compound of the chemical formula C4H5As. The structure is isoelectronic to that of pyrrole except that an arsenic atom is substituted for the nitrogen atom....


The 5-membered ring compounds containing two heteroatoms, at least one of which is nitrogen, are collectively called the azole
Azole

An azole is a class of five-membered nitrogen heterocyclic ring compounds containing at least one other noncarbon atom, nitrogen, sulfur or oxygen....
s. Thiazole
Thiazole

Thiazole, or 1,3-thiazole, is a clear to pale yellow flammable liquid with a pyridine-like odor and the molecular formula C3H3NS....
s and isothiazole
Isothiazole

An isothiazole is a type of organic compound containing a five-membered aromatic ring that consists of three carbon atoms, one nitrogen atom, and one sulfur atom....
s contain a sulfur and a nitrogen atom in the ring. Dithiolane
Dithiolane

A dithiolane is a sulfur heterocyclic compound derived from cyclopentane by replacing two methylene groups with thioether groups. The parent compounds are 1,2-dithiolane and 1,3-dithiolane....
s have two sulfur atoms.

Heteroatom Saturated Unsaturated
Nitrogen Imidazolidine
Imidazolidine

Imidazolidine is a heterocyclic compound formally derived by the addition of four hydrogen atoms to imidazole. The intermediate, resulting from the addition of only two hydrogen atoms is called dihydroimidazole....
Pyrazole
Pyrazole

Pyrazole refers both to the class of simple aromatic ring organic compounds of the heterocyclic series characterized by a 5-membered ring structure composed of three carbon atoms and two nitrogen atoms in adjacent positions and to the unsubstituted parent compound....
, Imidazole
Imidazole

Imidazole is a organic compound with the formula C3H4N2. This aromatic heterocyclic is classified as an alkaloid....
Nitrogen/oxygen Oxazolidine
Oxazolidine

Oxazolidine is a five-membered ring compound consisting of three carbons, a nitrogen, a hydrogen, and an oxygen. The oxygen and NH are the 1 and 3 positions, respectively....
Oxazole
Oxazole

Oxazole is the parent compound for a vast class of heterocyclic compound aromatic organic compounds. These are azoles with an oxygen and a nitrogen separated by one carbon....
, Isoxazole
Isoxazole

Isoxazole is an azole with an oxygen atom next to the nitrogen.Isoxazoles are found in some natural products, such as ibotenic acid. Isoxazoles also form the basis for a number of drugs, including the COX-2 inhibitor valdecoxib ....
Nitrogen/sulfur Thiazolidine
Thiazolidine

Thiazolidines are a class of heterocyclic organic compounds with a 5-membered saturation ring with an amine group and a thioether group in the 1 and 3 positions....
Thiazole
Thiazole

Thiazole, or 1,3-thiazole, is a clear to pale yellow flammable liquid with a pyridine-like odor and the molecular formula C3H3NS....
, Isothiazole
Isothiazole

An isothiazole is a type of organic compound containing a five-membered aromatic ring that consists of three carbon atoms, one nitrogen atom, and one sulfur atom....
Oxygen Dioxolane
Dioxolane

Dioxolane or 1,3-dioxolane is an Heterocyclic compound acetal with the chemical formula C3H6O2. It is an analogue of tetrahydrofuran with an additional ring oxygen atom and an analogue of the 6 membered ring dioxane....
 
Sulfur Dithiolane
Dithiolane

A dithiolane is a sulfur heterocyclic compound derived from cyclopentane by replacing two methylene groups with thioether groups. The parent compounds are 1,2-dithiolane and 1,3-dithiolane....
 


A large group of 5-membered ring compounds with three heteroatoms also exists. One example is dithiazoles that contain two sulfur and a nitrogen atom.

Heteroatom Saturated Unsaturated
Nitrogen  1,2,3-Triazole
1,2,3-Triazole

1,2,3-Triazole is one of a pair of isomeric chemical compounds with molecular formula C2H3N3, called triazoles, which have a five-membered ring of two carbon atoms and three nitrogen atoms....
, 1,2,4-Triazole
1,2,4-Triazole

1,2,4-Triazole is one of a pair of isomeric chemical compounds with molecular formula C2H3N3, called triazoles, which have a five-membered ring of two carbon atoms and three nitrogen atoms....
Nitrogen/2-sulfur  Dithiazole


Five-member ring compounds with four heteroatoms:

Heteroatom Saturated Unsaturated
Nitrogen  Tetrazole
Tetrazole

Tetrazoles are a class of chemical synthesis organic heterocyclic compound organic compound, consisting of a 5-member ring of four nitrogen and one carbon atom ....


With 5-heteroatoms, the compound may be considered inorganic rather than heterocyclic. Pentazole
Pentazole

Pentazole is an aromatic compound consisting of a five-membered ring with all nitrogen atoms, one of which is bonded to a hydrogen atom. It has a molecular formula of HN5....
 is the all nitrogen heteroatom unsaturated compound.

6-Membered rings


Six membered rings with a single heteroatom:

Heteroatom Saturated Unsaturated
Nitrogen Piperidine
Piperidine

Piperidine is an organic compound with the molecular formula 5NH. This heterocyclic compound amine consists of a six-membered ring containing five methylene units and one nitrogen atom....
Pyridine
Pyridine

Pyridine is a simple and important heterocyclic aromatic organic compound with the formula CarbonHydrogenNitrogen. This colorless liquid with a distinctive fish-like odor is structurally related to benzene, wherein one CH group in the six-membered ring is replaced by a nitrogen atom....
Oxygen Tetrahydropyran
Tetrahydropyran

Tetrahydropyran, or oxane, is the organic compound consisting of a saturated six-membered ring containing five carbon atoms and one oxygen atom....
Pyran
Pyran

In chemistry, a pyran is a six membered heterocyclic ring consisting of five carbon atoms and one oxygen atom and containing two double bonds. The molecular formula is C5H6O....
Sulfur Thiane Thiine (thiapyrane)


With two heteroatoms:

Heteroatom Saturated Unsaturated
Nitrogen Piperazine
Piperazine

Piperazine is an organic compound that consists of a six-membered ring containing two opposing nitrogen atoms. Piperazine exists as small alkaline deliquescent crystals with a salt taste....
Diazine
Diazine

Diazine refers to a group of organic compounds having the molecular formula C4H4N2. Each contains a benzene ring in which two of the C-H fragments have been replaced by isolobal nitrogen....
s
Nitrogen / oxygen Oxazine 
Nitrogen / sulfur Thiazine
Thiazine

Thiazines are organic compounds containing a ring of four carbon, one nitrogen and one sulfur atom. Chemicals that include thiazine are used for dyes, tranquilizers and insecticides....
Sulfur Dithiane
Dithiane

A dithiane is a heterocyclic compound composed of a cyclohexane core structure with two methylene units replaced by sulfur. The parent compounds are 1,2-dithiane, 1,3-dithiane and 1,4-dithiane....
 
Oxygen Dioxane Dioxin


With three heteroatoms:

Heteroatom Saturated Unsaturated
Nitrogen  Triazine
Triazine

A triazine is one of three organic chemicals, isomeric with each other, whose empirical formula is 333....
Oxygen Trioxane
Trioxane

Trioxane refers to a pair of isomeric organic compounds having the molecular formula C3H6O3. Each contains a six membered ring with three carbon atoms and three oxygen atoms....
 


With four heteroatoms:

Heteroatom Saturated Unsaturated
Nitrogen  Tetrazine
Tetrazine

Tetrazine is an unstable Chemical compound that consists of a six-membered aromatic ring containing four nitrogen atoms with the molecular formula Carbon2Hydrogen2Nitrogen4....


The hypothetical compound with six nitrogen heteroatoms would be hexazine
Hexazine

Hexazine is a hypothetical allotrope of nitrogen composed of 6 nitrogen atoms arranged in a ring-like structure analogous to that of benzene. It would be the final member of the azabenzene series, having all of the methylidyne groups of the benzene molecule replaced with nitrogen atoms....
.

7-Membered rings

With 7-membered rings, aromatic stabilization is not available. Compounds with one heteroatom include:

Heteroatom Saturated Unsaturated
Nitrogen  Azepine
Sulfur  Thiepin
Thiepin

In organic chemistry, thiepine is an Saturation seven-membered heterocyclic compound, with six carbon atoms and one sulfur atom.Benzothiepines have one fused benzene group and dibenzothiepines such as dosulepin hydrochloride and zotepine have two fused benzene groups....


Those with two heteroatoms include:

Heteroatom Saturated Unsaturated
Nitrogen  Diazepine
Diazepine

Diazepine is a seven-membered heterocyclic compound with two nitrogen atoms and three double bonds.When combined with a benzene ring, it is the basis of the benzodiazepine family of compounds....


Fused rings

Heterocyclic rings systems that are formally derived by fusion with other rings, either carbocyclic or heterocyclic, have a variety of common and systematic names. For example, with the benzo-fused unsaturated nitrogen heterocycles, pyrrole provides indole
Indole

Indole is an aromatic Heterocyclic compound organic compound. It has a bicyclic structure, consisting of a six-membered benzene ring fused to a five-membered nitrogen-containing pyrrole ring....
 or isoindole
Isoindole

Isoindole in heterocyclic chemistry is a arene compound fused pyrrole. The compound is an isomer of indole and its organic reduction form is an isoindoline....
 depending on the orientation. The pyridine analog is quinoline
Quinoline

Quinoline, also known as 1-azanaphthalene, 1-benzazine, or benzo[b]pyridine, is a heterocyclic aromatic organic compound. It has the formula C9H7N and is a colourless hygroscopic liquid with a strong odour....
 or isoquinoline
Isoquinoline

Isoquinoline, also known as benzo[c]pyridine or 2-benzanine, is a heterocyclic aromatic organic compound. It is a structural isomer of quinoline....
. For azepine, benzazepine
Benzazepines

Benzazepines are heterocyclic compounds consisting of a benzene ring fused to an azepine ring. Examples include fenoldopam, and galantamine....
 is the preferred name. Similarly, the compounds with two benzene rings fused to the central heterocycle are carbazole
Carbazole

Carbazole is an aromatic Heterocyclic compound organic compound. It has a tricyclic structure, consisting of two six-membered benzene ring fused on either side of a five-membered nitrogen-containing ring....
, acridine
Acridine

Acridine, C13H9N, is an organic compound and a heterocyclic compound. Acridine is also used to describe compounds containing the C13N tricycle....
, and dibenzoazepine.

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