AskDefine | Define heterocyclic

Dictionary Definition

heterocyclic adj : containing a closed ring of atoms of which at least one is not a carbon atom n : a compound containing a heterocyclic ring [syn: heterocyclic compound, heterocycle]

User Contributed Dictionary



  1. Of a cyclic compound that contains one or more atoms other than carbon in at least one of its rings.


of cyclic compounds: containing one or more atoms other than carbon
  • Italian: eterociclico

Extensive Definition

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 prefix 'cyclic' implies a ring structure, whereas 'hetero' refers to an atom other than carbon, as above. Many heterocyclic compounds, including some amines, are carcinogenic.
Heterocyclic chemistry is the chemistry branch dealing exclusively with synthesis, properties, and applications of heterocycles.

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 are:

4-Membered rings

5-Membered rings

With heterocycles containing five atoms, the unsaturated compounds are frequently more stable because of aromaticity.
A large group of 5-membered ring compounds with two heteroatoms are collectively called the azoles. Dithiolanes have two sulfur atoms.

6-Membered rings

Six membered rings with a single heteroatom:
With two heteroatoms:

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. 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.


heterocyclic in Arabic: حلقة غير متجانسة
heterocyclic in Catalan: Compost heterocíclic
heterocyclic in Czech: Heterocyklické sloučeniny
heterocyclic in German: Heterocyclen
heterocyclic in Spanish: Compuesto heterocíclico
heterocyclic in French: Hétérocycle
heterocyclic in Italian: Composto eterociclico
heterocyclic in Hebrew: תרכובת הטרוציקלית
heterocyclic in Macedonian: Хетероциклично соединение
heterocyclic in Dutch: Heterocyclische verbinding
heterocyclic in Japanese: 複素環式化合物
heterocyclic in Polish: Związki heterocykliczne
heterocyclic in Portuguese: Composto heterocíclico
heterocyclic in Russian: Гетероциклические соединения
heterocyclic in Slovak: Heterocyklická zlúčenina
heterocyclic in Finnish: Heterosyklinen yhdiste
heterocyclic in Swedish: Heterocykliska föreningar
heterocyclic in Ukrainian: Гетероциклічні сполуки
heterocyclic in Chinese: 杂环化合物
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