- Heterocyclic compound
Heterocyclic compounds are
organic compounds containing at least one atom of carbon, and at least one element other than carbon, such as sulfur, oxygenor nitrogenwithin a "ring structure".cite book
author = Eicher, T.; Hauptmann, S.
title = The Chemistry of Heterocycles: Structure, Reactions, Syntheses, and Applications
publisher = Wiley-VCH
date = 2nd ed. 2003
id = ISBN 3527307206 ] These structures may comprise 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.
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:
A large group of 5-membered ring compounds with two heteroatoms are collectively called the
azoles. Dithiolanes have two sulfur atoms.
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 acidsand 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. [cite web | title = Heterocyclic Amines in Cooked Meats | date = 15 Sep 2004 | publisher = National Cancer Institute | accessdate = 2007-08-09 | url = http://www.cancer.gov/cancertopics/factsheet/Risk/heterocyclic-amines] NCI's Division of Cancer Epidemiology and Genetics found a link between individuals with stomach cancerand the consumption of cooked meat, and other studies for colorectal, pancreatic, and breast canceris 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.
* [http://www.chem.qmul.ac.uk/iupac/hetero/HW.html Nomenclature, IUPAC]
* [http://www.cancer.gov/cancertopics/factsheet/Risk/heterocyclic-amines Heterocyclic amines in cooked meat, US CDC]
* [http://www.cancer.org/docroot/PED/content/PED_1_3x_Known_and_Probable_Carcinogens.asp List of known and probable carcinogens, American Cancer Society]
* [http://www.scorecard.org/chemical-groups/one-list.tcl?short_list_name=p65 List of known carcinogens by the State of California,
Proposition 65] (more comprehensive)
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