Heterocyclic_compound

Various representations of a molecule of pyridine. The hexagonal ring is composed of five carbon atoms (at the five unmarked corners) and one nitrogen atom (marked with an N).
Heterocyclic compounds are organic compounds that contain a ring structure containing atoms in addition to carbon, such as sulfur, oxygen or nitrogen, as part of the ring. They may be either simple aromatic rings or non-aromatic rings. Some examples are pyridine (C5H5N), pyrimidine (C4H4N2) and dioxane (C4H8O2).
Note that compounds such as cyclopropane, an anaesthetic with explosive properties, and cyclohexane, a solvent, are not heterocyclic, they are merely cycloalkanes. The suffix '-cyclic' implies a ring structure, while 'hetero' refers to an atom other than carbon, as above. Many heterocyclic compounds, including some amines, are carcinogenic.

Contents

1 3-membered rings
2 4-membered rings
3 5-membered rings
4 6-membered rings
5 Heterocyclic amines and cancer
6 See also
7 Notes
8 References
9 External links
10 Credits



Heterocyclic chemistry is the chemistry branch dealing exclusively with synthesis, properties and applications of heterocycles especially vital to drug design.

 Various representations of a molecule of pyrimidine. The hexagonal ring is composed of four carbon atoms (at the four unmarked corners) and two nitrogen (N) atoms.
 A molecule of 1,4-dioxane has two oxygen (O) atoms in its ring structure.
3-membered rings
Heterocycles with three atoms in the ring are more reactive because of ring strain. Those containing one heteroatom are generally stable. Those with two heteroatoms are more likely to occur as reactive intermediates. Common 3-membered heterocycles are:



heteroatom

saturated

unsaturated


Nitrogen

aziridine




Oxygen

ethylene oxide (epoxides, oxiranes)

oxirene


Sulphur

thiirane (episulfides)



4-membered rings


heteroatom

saturated

unsaturated


Nitrogen

azetidine




Oxygen

oxetane



5-membered rings
With heterocycles containing five atoms, the unsaturated compounds are frequently more stable because of aromaticity.



heteroatom

saturated

unsaturated


Nitrogen

dihydropyrrole (pyrroline) & tetrahydropyrrole (pyrrolidine)

pyrrole


Oxygen

dihydrofuran & tetrahydrofuran

furan


Sulphur

dihydrothiophene & tetrahydrothiophene

thiophene (thiole)


Arsenic



arsole

With two heteroatoms:

The azoles:
Two N: pyrazole & imidazole
Three N: triazole
Four N: tetrazole
One N and one O: oxazole & isoxazole
One N and one S: thiazole & isothiazole
Two S: Dithiolane
6-membered rings


heteroatom

saturated

unsaturated


Nitrogen

piperidine

pyridine


Oxygen

tetrahydropyran

pyran


Sulphur

Thiane

Thiine aka thiapyrane

With two heteroatoms:

Two N: Pyridazine, Pyrimidine, and Pyrazine are the 1,2-, 1,3-, and 1,4-isomers, respectively.
Two N: Piperazine
One N and one O: Oxazines
One N and one S: Thiazine
Two S: Dithiane
Two O: Dioxane
Heterocyclic amines and cancer
Some heterocyclic amines (HCAs) found in cooked meat are known carcinogens. Research has shown that cooking certain meats at high temperatures creates chemicals that are not present in uncooked meats. For example, heterocyclic amines are the carcinogenic chemicals formed from the cooking of muscle meats such as beef, pork, fowl, and fish. HCAs form when amino acids and creatine (a chemical found in muscles) react at high cooking temperatures. Researchers have identified 17 different HCAs resulting from the cooking of muscle meats that may pose human cancer risk.[1] NCI's Division of Cancer Epidemiology and Genetics found a link between individuals with stomach cancer and the consumption of cooked meat, and other studies for colorectal, pancreatic, and breast cancer is associated with high intakes of well-done, fried, or barbecued meats. Other sources of protein (milk, eggs, tofu, and organ meats such as liver) have very little or no HCA content naturally or when cooked.

See also
Pyridine
Pyrimidine
Notes

↑ Heterocyclic Amines in Cooked Meats National Cancer Institute. Retrieved December 10, 2007.


ReferencesISBN links support NWE through referral fees
Eicher, Theophil, Siegfried Hauptmann, and Andreas Speicher. 2003. The Chemistry of Heterocycles: Structure, Reactions, Syntheses, and Applications. Weinheim: Wiley-VCH. ISBN 3527307206
Joule, J. A., and K. Mills. 2000. Heterocyclic Chemistry. 4th ed. Malden, MA: Blackwell Science. ISBN 0632054530
McMurry, John. 2004. Organic Chemistry. 6th ed. Belmont, CA: Brooks/Cole. ISBN 0534420052
Morrison, Robert T., and Robert N. Boyd. 1992. Organic Chemistry. 6th ed. Englewood Cliffs, NJ: Prentice Hall. ISBN 0-13-643669-2
Solomons, T.W. Graham, and Craig B. Fryhle. 2004. Organic Chemistry. 8th ed. Hoboken, NJ: John Wiley. ISBN 0471417998
External links
All links retrieved December 22, 2017.

Heterocyclic amines in cooked meat, US CDC
List of known carcinogens by the State of California, Proposition 65

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