free radicaln.
/ˌfriː ˈradᵻkl/, U.S. /ˌfri ˈrædək(ə)l/ Chemistry.
Originally: a group or radical (radical n. 5a) in an uncombined state. Now: spec. an uncharged atom or group of atoms having one or more unpaired electrons, esp. when these normally form part of a bond.Free radicals are typically highly reactive, and in the body may be the cause of damage to molecules such as DNA and proteins.
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the world > matter > chemistry > chemical bonding > [noun] > bonds > free radical
free radical1870
radical1900
1870 Proc. Royal Soc. 1869–70 18 349 The author found it extremely desirable..to trace the modifications undergone by nitryl as it is transmitted (from the chloride, hydrate, or free radical) through an adequate succession of combinations.
1886 E. F. Smith tr. V. von Richter Chem. Carbon Compounds 200 The free acid radicals, like all monovalent groups, cannot exist free.]
1900 Jrnl. Amer. Chem. Soc. 22 768 We have to deal here with a free radical, triphenylmethyl.
1948 W. A. Waters Chem. Free Radicals (ed. 2) i. 4 The great chemical activity of the free radicals is to be associated with available combining energy of the odd electron.
1971 Nature 12 Feb. 500/1 The presence of free radicals in cigarette smoke was demonstrated by Lyons et al.
1984 A. Hailey Strong Medicine ii. vii. 159 Vincent Lord knew that many drugs, when in action in the human body and as part of their metabolism, generated ‘free radicals’.
1985 Health News (Sydney) Aug.–Oct. 3/1 (heading) The culprits in ageing—free radicals.
2006 Daily Tel. 19 June 26/4 Curcumin Complex, an extract of turmeric,..is a potent antioxidant—to mop up cancer-causing free radicals.
Compounds
C1. General attributive.Some of the more established compounds of this type are treated separately at Compounds 2.
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1921 Science 8 July 36/2 The theory that the color of free radical solutions is due to dissociation of the dimolecular to the monomolecular form.
1934 Proc. Royal Soc. A. 146 263 The free radical theory appears to rest mainly on the analyses with methyl ethyl ketone.
1967 D. Margerison & G. C. East Introd. Polymer Chem. iv. 152 The only types of reaction which occur in free radical polymerization.
1977 J. March Adv. Org. Chem. (ed. 2) xv. 733 These reactions are catalyzed by free-radical initiators and inhibited by galvinoxyl (a free-radical inhibitor).
1993 Dog World Oct. 37/2 To prevent rancidity, one has to prevent oxidation and free-radical generation.
2001 Chemicals & Materials from Renewable Resources (ACS Symp. Ser. No. 784) viii. 104 No accompanying free radical photoreactions were detected.
C2.
free-radical damage n.
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1961 Biochimica et Biophysica Acta 52 607 An attempt to detect free-radical damage in the vitamin E-deficient chick.
1984 Listener 17 May 8/1 To prevent free-radical damage, our bodies produce scavenger enzymes that act as antioxidants.
2003 Guardian 5 Apr. (Weekend Suppl.) 49/1 Liver spots..are an external sign of extensive free radical damage.
free-radical mechanism n.
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1937 Proc. Royal Soc. A. 163 540 It is evidently a polymerization occurring by means of the free radical mechanism.
1998 S. W. Moore in R. C. Hamdy et al. Alzheimer's Dis. (ed. 3) xiv. 188 It may also contribute to preservation of surviving neurons from neurotoxins that use oxidative/free radical mechanisms.
free-radical scavenger n.
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1957 U.S. Patent 2,786,044 5 They also serve as antioxidants and resin stabilizers by acting as free radical scavengers.
2000 Here's Health May 75/1 These microspheres contain a blend of organic carrot juice, which prevents the formation of free-radicals, and a free-radical scavenger derived from red wine.
free-radical scavenging n. and adj.
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1965 Radiation Res. 24 184 (title) Macromolecular repair and free radical scavenging in the protection of bacteria against X-rays.
1991 Saudi Med. Jrnl. 12 89/2 Captopril , an angiotensin converting enzyme inhibitor, also has some free radical scavenging properties.
1993 Brit. Jrnl. Surg. 80 114/1 Oxygen free radical scavenging agents also diminish the severity of this vascular lesion.
2000 Big Issue 10 Apr. 2/1 (advt.) Antioxidants and free radical scavenging nutrients: the key to optimal health.
This entry has been updated (OED Third Edition, June 2008; most recently modified version published online March 2022).
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n.1870