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1/29/2016 - Wikipedia, the free encyclopedia Heterocyclic compound From Wikipedia, the free encyclopedia

A heterocyclic compound or ring structure is a that has atoms of at least two different elements as members of its ring(s).[1] Heterocyclic chemistry is the branch of chemistry dealing with the synthesis, properties and applications of these heterocycles. In contrast, the rings of homocyclic compounds consist entirely of atoms of the same element.

Although heterocyclic compounds may be inorganic, most contain at least one . While atoms that are neither carbon nor hydrogen are normally referred to in as , this is usually in comparison to the all-carbon backbone. But this does not prevent a compound such as borazine (which has no , a carbon atoms) from being labelled "heterocyclic". IUPAC recommends the Hantzsch- heterocyclic Widman nomenclature for naming heterocyclic compounds. compound

Contents

1 Classification based on electronic structure cyclo-octasulfur, a 2 3-membered rings homocyclic compound

3 4-membered rings

4 5-membered rings

5 6-membered rings

6 7-membered rings

7 8-membered rings

8 9-membered rings

9 Images

10 Fused rings

11 History of heterocyclic chemistry

12 Commercial use

13 References

14 External links

https://en.wikipedia.org/wiki/Heterocyclic_compound 1/8 1/29/2016 Heterocyclic compound - Wikipedia, the free encyclopedia Classification based on electronic structure

Heterocyclic compounds can be usefully classified based on their electronic structure. The saturated heterocycles behave like the acyclic derivatives. Thus, piperidine and are conventional amines and ethers, with modified steric profiles. Therefore, the study of heterocyclic chemistry focuses especially on unsaturated derivatives, and the preponderance of work and applications involves unstrained 5- and 6- membered rings. Included are pyridine, , , and . Another large class of heterocycles are fused to rings, which for pyridine, thiophene, pyrrole, and furan are , , , and , respectively. Fusion of two benzene rings gives rise to a third large family of compounds, respectively the , dibenzothiophene, , and dibenzofuran. The unsaturated rings can be classified according to the participation of the in the pi system. 3-membered rings

Heterocycles with three atoms in the ring are more reactive because of ring strain. Those containing one heteroatom are, in general, stable. Those with two heteroatoms are more likely to occur as reactive intermediates. Common 3-membered heterocycles with one heteroatom are:

Heteroatom Saturated Unsaturated Azirine Oxirane (, Oxirene ) (episulfides) Thiirene

Those with two heteroatoms include:

Heteroatom Saturated Unsaturated Nitrogen Diazirine Nitrogen/oxygen Oxaziridine Oxygen

4-membered rings

Compounds with one heteroatom:

Heteroatom Saturated Unsaturated Nitrogen Azetidine Azete Oxygen Oxetane Oxete Sulfur Thietane Thiete

Compounds with two heteroatoms:

https://en.wikipedia.org/wiki/Heterocyclic_compound 2/8 1/29/2016 Heterocyclic compound - Wikipedia, the free encyclopedia Heteroatom Saturated Unsaturated Nitrogen Diazetidine Oxygen Dioxetane Dioxete Sulfur Dithietane Dithiete

5-membered rings

With heterocycles containing five atoms, the unsaturated compounds are frequently more stable because of .

Five-membered rings with one heteroatom:

Heteroatom Saturated Unsaturated Nitrogen Pyrrolidine (Azolidine is not used) Pyrrole ( is not used) Oxygen Tetrahydrofuran (Oxolane is rare) Furan (Oxole is not used) Sulfur Thiolane Thiophene (Thiole is not used) Borolane Borole Phospholane Arsolane Stibolane Stibole Bismolane Silolane Silole Stannolane Stannole

The 5-membered ring compounds containing two heteroatoms, at least one of which is nitrogen, are collectively called the . Thiazoles and isothiazoles contain a sulfur and a nitrogen atom in the ring. Dithiolanes have two sulfur atoms.

Unsaturated (and partially Heteroatom Saturated unsaturated) Nitrogen/nitrogen Imidazolidine (Imidazoline) Pyrazolidine (Pyrazoline) Nitrogen/oxygen () Isoxazolidine Nitrogen/sulfur Thiazolidine Thiazole () Isothiazolidine Isothiazole Oxygen/oxygen Dioxolane Sulfur/sulfur 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.

https://en.wikipedia.org/wiki/Heterocyclic_compound 3/8 1/29/2016 Heterocyclic compound - Wikipedia, the free encyclopedia Heteroatom Saturated Unsaturated 3 × Nitrogen Furazan 2 × Nitrogen / 1 × oxygen Oxadiazole 2 × Nitrogen / 1 × sulfur Thiadiazole 1 × Nitrogen / 2 × sulfur Dithiazole

Five-member ring compounds with four heteroatoms:

Heteroatom Saturated Unsaturated 4 × Nitrogen

With 5-heteroatoms, the compound may be considered inorganic rather than heterocyclic. is the all nitrogen heteroatom unsaturated compound. 6-membered rings

Six-membered rings with a single heteroatom:

Heteroatom Saturated Unsaturated Piperidine (Azinane is not Nitrogen Pyridine ( is not used) used) Oxygen Oxane (2H-Oxine is not used) Thiopyran (2H-Thiine is not Sulfur Thiane used) Silicon Salinane Siline Germinane Germine Tin Stanninane Stannine Boron Borinane Borinine Phosphorus Phosphinane Phosphinine Arsenic Arsinane Arsinine

With two heteroatoms:

Heteroatom Saturated Unsaturated Nitrogen / nitrogen Oxygen / nitrogen Oxazine Sulfur / nitrogen Thiazine Oxygen / oxygen Dioxane Dioxine Sulfur / sulfur Dithiane Dithiine

With three heteroatoms: https://en.wikipedia.org/wiki/Heterocyclic_compound 4/8 1/29/2016 Heterocyclic compound - Wikipedia, the free encyclopedia Heteroatom Saturated Unsaturated Nitrogen Oxygen Trioxane Sulfur Trithiane

With four heteroatoms:

Heteroatom Saturated Unsaturated Nitrogen

The hypothetical compound with six nitrogen heteroatoms would be . 7-membered rings

With 7-membered rings, the heteroatom must be able to provide an empty pi orbital (e.g., boron) for "normal" aromatic stabilization to be available; otherwise, homoaromaticity may be possible. Compounds with one heteroatom include:

Heteroatom Saturated Unsaturated Nitrogen Azepane Azepine Oxygen Oxepane Oxepine Sulfur Thiepane Thiepine

Those with two heteroatoms include:

Heteroatom Saturated Unsaturated Nitrogen Homopiperazine Diazepine Nitrogen/sulfur Thiazepine

8-membered rings

Heteroatom Saturated Unsaturated Nitrogen Azocane Azocine Sulfur

9-membered rings

Heteroatom Saturated Unsaturated Nitrogen Azonane Oxygen Oxonane Oxonine Sulfur Thionane Thionine

https://en.wikipedia.org/wiki/Heterocyclic_compound 5/8 1/29/2016 Heterocyclic compound - Wikipedia, the free encyclopedia Images

Names in italics are retained by IUPAC and they do not follow the Hantzsch-Widman nomenclature

Saturated Unsaturated Heteroatom Nitrogen Oxygen Sulfur Nitrogen Oxygen Sulfur Aziridine Oxirane Thiirane Azirine Oxirene Thiirene

3-Atom Ring

Azetidine Oxetane Thietane Azete Oxete Thiete

4-Atom Ring

Pyrrolidine Oxolane Thiolane Pyrrole Furan Thiophene

5-Atom Ring

Piperidine Oxane Thiane Pyridine Pyran Thiopyran

6-Atom Ring

Azepane Oxepane Thiepane Azepine Oxepine Thiepine

7-Atom Ring

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 or depending on the orientation. The pyridine analog is quinoline or isoquinoline. For azepine, benzazepine is the preferred name. Likewise, the compounds with two benzene rings fused to the central heterocycle are carbazole, acridine, and dibenzoazepine.

https://en.wikipedia.org/wiki/Heterocyclic_compound 6/8 1/29/2016 Heterocyclic compound - Wikipedia, the free encyclopedia History of heterocyclic chemistry

The history of heterocyclic chemistry began in the 1800s, in step with the development of organic chemistry. Some noteworthy developments:[2] 1818: Brugnatelli isolates alloxan from 1832: Dobereiner produces furfural (a furan) by treating starch with sulfuric acid 1834: Runge obtains pyrrole ("fiery oil") by dry distillation of bones 1906: Friedlander synthesizes indigo dye, allowing synthetic chemistry to displace a large agricultural industry 1936: Treibs isolates chlorophyl derivatives from crude oil, explaining the biological origin of petroleum. 1951: Chargaff's rules are described, highlighting the role of heterocyclic compounds (purines and ) in the genetic code. Commercial use

Leading companies with a vast number of patents related to heterocyclic compounds are Bayer, Merck, Ciba- Geigy, Pfizer, Eli Lily, BASF, Hoffmann La Roche, ER Sqibb, Warner Lambert and Hoechst.[3] References

1. IUPAC Gold Book heterocyclic compounds (http://goldbook.iupac.org/H02798.html) 2. E. Campaigne "Adrien Albert and the Rationalization of Heterocyclic Chemistry" J. Chemical Education 1986, Volume 6, 860. doi:10.1021/ed063p860 (https://dx.doi.org/10.1021%2Fed063p860) 3. Companies with the highest number of patents related to heterocyclic compounds. (http://www.ipexl.com/share/f593e64bc3679cb669d02c007efdca17) External links

Hantzsch-Widman nomenclature, IUPAC Wikimedia Commons has (http://www.chem.qmul.ac.uk/iupac/hetero/HW.html) media related to heterocyclic Heterocyclic amines in cooked meat, US CDC compounds.

Wikiquote has quotations related to: Heterocyclic compound (http://www.cancer.gov/cancertopics/factsheet/Risk/heterocyclic-amines) List of known and probable carcinogens, American Cancer Society (http://www.cancer.org/docroot/PED/content/PED_1_3x_Known_and_Probable_Carcinogens.asp) List of known carcinogens by the State of California, (http://www.scorecard.org/chemical-groups/one- list.tcl?short_list_name=p65) Proposition 65 (more comprehensive)

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Categories: Heterocyclic compounds

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