|
Search over 100 encyclopedias and dictionaries: |
Research categories | Follow us on Twitter |
Research categories
View all topics in the newsView all reference sources at Encyclopedia.com |
|||
free radical
free radical in chemistry, a molecule or atom that contains an unpaired electron but is neither positively nor negatively charged. Free radicals are usually highly reactive and unstable. They are produced by homolytic cleavage of a covalent bond (see chemical bond ); i.e., each of the atoms connected by the bond retains one of the two electrons making up the bond. The homolytic cleavage of a hydrogen molecule, H 2 , produces two hydrogen free radicals (hydrogen atoms). Similarly, two chlorine free radicals can be produced from a chlorine molecule. Homolytic cleavage of the carbon-bromine bond in methyl bromide, CH 3 Br, would produce a methyl free radical and a bromine free radical. The term free is often dropped in referring to free radicals; this could lead to confusion if the term radical were used synonymously with group in organic chemistry, e.g., by calling an alkyl group an alkyl radical when free radical was not intended. |
|
|
Cite this article
"free radical." The Columbia Encyclopedia, 6th ed.. 2011. Encyclopedia.com. 29 May. 2012 <http://www.encyclopedia.com>. "free radical." The Columbia Encyclopedia, 6th ed.. 2011. Encyclopedia.com. (May 29, 2012). http://www.encyclopedia.com/doc/1E1-freeradi.html "free radical." The Columbia Encyclopedia, 6th ed.. 2011. Retrieved May 29, 2012 from Encyclopedia.com: http://www.encyclopedia.com/doc/1E1-freeradi.html |
|
free radical
free radical An atom or group of atoms with an unpaired valence electron. Free radicals are formed when a bond is broken without forming ions. Because of their unpaired electrons, most free radicals are extremely reactive. For example, superoxide free radicals, formed in the body during normal metabolic processes and as a reaction to toxins and infections, have damaging effects on cells and tissues. See also antioxidants; superoxide dismutase.
|
|
|
Cite this article
"free radical." A Dictionary of Biology. 2004. Encyclopedia.com. 29 May. 2012 <http://www.encyclopedia.com>. "free radical." A Dictionary of Biology. 2004. Encyclopedia.com. (May 29, 2012). http://www.encyclopedia.com/doc/1O6-freeradical.html "free radical." A Dictionary of Biology. 2004. Retrieved May 29, 2012 from Encyclopedia.com: http://www.encyclopedia.com/doc/1O6-freeradical.html |
|
free radical
free rad·i·cal • n. Chem. an uncharged molecule (typically highly reactive and short-lived) having an unpaired valence electron. |
|
|
Cite this article
"free radical." The Oxford Pocket Dictionary of Current English. 2009. Encyclopedia.com. 29 May. 2012 <http://www.encyclopedia.com>. "free radical." The Oxford Pocket Dictionary of Current English. 2009. Encyclopedia.com. (May 29, 2012). http://www.encyclopedia.com/doc/1O999-freeradical.html "free radical." The Oxford Pocket Dictionary of Current English. 2009. Retrieved May 29, 2012 from Encyclopedia.com: http://www.encyclopedia.com/doc/1O999-freeradical.html |
|
Search over 100 encyclopedias and dictionaries:
HighBeam™ Research, Inc. © Copyright 2012. All rights reserved.
The Encyclopedia.com advertising network includes:
