Fluoride 155650 224962389 2008-07-11T05:34:34Z NickBush24 309097 Reverted edits by [[Special:Contributions/144.131.188.113|144.131.188.113]] to last version by Closedmouth (using [[WP:HG|Huggle]]) :''This article is about the chemical ion F&nbsp;<sup>&minus;</sup>. For the addition of fluoride ions to water supplies, see [[Water fluoridation]].'' '''Fluoride''' is the reduced form of [[fluorine]]. Both [[organic compounds|organic]] and [[inorganic]] compounds containing the [[chemical element|element]] fluorine are considered fluorides. As a [[halogen]], fluorine forms a monovalent ion (−1 charge). The range of fluorides is considerable as fluorine forms compounds with all elements except He and Ne<ref>{{Greenwood&Earnshaw}} p. 804</ref><ref>{{cite journal | last = Khriachtchev | first = Leonid | coauthors = Mika Pettersson, Nino Runeberg, Jan Lundell & Markku Räsänen | date = [[24 August]] [[2000]] | title = A stable argon compound | journal = Nature | volume = 406 | pages = 874–876 | doi = 10.1038/35022551 | url = http://www.nature.com/nature/journal/v406/n6798/abs/406874a0.html }}</ref>. Fluorides range from severe toxins such as [[sarin]] to life-saving pharmaceuticals such as [[efavirenz]] and from refractory materials such as [[calcium fluoride]] to highly reactive [[sulfur tetrafluoride]]. ==Occurrence== [[Image:USDA Mineral Flourite 93c3962.jpg|thumb|right|The [[mineral]] [[fluorite]].]] Solutions of inorganic fluorides in water contain F<sup>−</sup> and [[bifluoride]] HF<sub>2</sub><sup>−</sup>.<ref>Holleman, A. F.; Wiberg, E. "Inorganic Chemistry" Academic Press: San Diego, 2001. ISBN 0-12-352651-5.</ref> Few inorganic fluorides are soluble in water without undergoing significant hydrolysis. Examples of inorganic fluorides include [[hydrofluoric acid]] (HF), [[sodium fluoride]] (NaF), and [[uranium hexafluoride]] (UF<sub>6</sub>). In terms of its reactivity, fluoride differs significantly from [[chloride]] and other halides, and is more strongly solvated due to its smaller radius/charge ratio. Its closest chemical relative is [[hydroxide]]. The Si-F linkage is one of the strongest single bonds. In contrast, other silyl halides are easily hydrolyzed. Many fluoride minerals are known, but paramount in commercial importance are [[fluorite]] and [[fluoroapatite]]. Fluoride is found naturally in low concentration in drinking water and foods. Water with underground sources is more likely to have higher levels of fluoride, whereas the concentration in seawater averages 1.3 [[parts per million]] (ppm).<ref>[http://www.who.int/water_sanitation_health/dwq/chemicals/fluoride.pdf Fluoride in Drinking-water: Background document for development of WHO Guidelines for Drinking-water Quality]. World Health Organization, 2004, page 2. Page accessed on February 22, 2007.</ref> Fresh water supplies generally contain between 0.01-0.3 ppm, while the ocean contains between 1.2 and 1.5 ppm.<ref>[http://www.inchem.org/documents/ehc/ehc/ehc227.htm#5.0 Environmental Health Criteria 227: Fluorides]. World Health Organization, 2002, page 38. Page accessed on February 22, 2007.</ref> ==Applications== Fluorides are pervasive in modern technology. [[Hydrofluoric acid]] is the most important fluoride synthesized. It is principally used in the production of fluorocarbons and aluminium fluorides. Hydrofluoric acid has a variety of specialized applications, including its ability to dissolve glass.<ref name=Aigueperse>Jean Aigueperse, Paul Mollard, Didier Devilliers, Marius Chemla, Robert Faron, Renée Romano, Jean Pierre Cuer, “Fluorine Compounds, Inorganic” in Ullmann’s Encyclopedia of Industrial Chemistry 2005 Wiley-VCH, Weinheim. DOI 10.1002/14356007.a11 307</ref> ===Organic synthesis=== Fluoride reagents are significant in [[organic synthesis|synthetic]] [[organic chemistry]]. Due to the affinity of [[silicon]] for fluoride, and the ability of silicon to expand its coordination number, [[silyl ether]] [[protecting group]]s can be easily removed by the fluoride sources such as [[sodium fluoride]] and [[tetra-n-butylammonium fluoride]] (TBAF). ===Enzyme inhibitors=== In [[biochemistry]], fluoride salts are commonly used to [[enzyme inhibitor|inhibit]] the activity of [[phosphatases]], such as [[serine]]/[[threonine]] phosphatases.<ref>{{cite journal |author=Nakai C, Thomas JA |title=Properties of a phosphoprotein phosphatase from bovine heart with activity on glycogen synthase, phosphorylase, and histone |journal=J. Biol. Chem. |volume=249 |issue=20 |pages=6459–67 |year=1974 |pmid=4370977 |doi= |url=http://www.jbc.org/cgi/pmidlookup?view=long&pmid=4370977}}</ref> It may do this by replacing the [[nucleophile|nucleophilic]] [[hydroxyl ion]] in these enzymes' active sites.<ref>{{cite journal |author=Schenk G, Elliott TW, Leung E, ''et al'' |title=Crystal structures of a purple acid phosphatase, representing different steps of this enzyme's catalytic cycle |journal=BMC Struct. Biol. |volume=8 |issue=1 |pages=6 |year=2008 |pmid=18234116 |doi=10.1186/1472-6807-8-6 |url=http://www.biomedcentral.com/1472-6807/8/6}}</ref> [[Beryllium fluoride]] and [[aluminium fluoride]] are also used as phosphatase inhibitors, since these compounds are structural mimics of the [[phosphate]] group and can act as analogues of the [[transition state]] of the reaction.<ref>{{cite journal |author=Wang W, Cho HS, Kim R, ''et al'' |title=Structural characterization of the reaction pathway in phosphoserine phosphatase: crystallographic "snapshots" of intermediate states |journal=J. Mol. Biol. |volume=319 |issue=2 |pages=421–31 |year=2002 |pmid=12051918 |doi=10.1016/S0022-2836(02)00324-8 |url=http://linkinghub.elsevier.com/retrieve/pii/S0022-2836(02)00324-8}}</ref><ref>{{cite journal |author=Cho H, Wang W, Kim R, ''et al'' |title=BeF(3)(-) acts as a phosphate analog in proteins phosphorylated on aspartate: structure of a BeF(3)(-) complex with phosphoserine phosphatase |journal=Proc. Natl. Acad. Sci. U.S.A. |volume=98 |issue=15 |pages=8525–30 |year=2001 |pmid=11438683 |doi=10.1073/pnas.131213698 |url=http://www.pnas.org/cgi/pmidlookup?view=long&pmid=11438683}}</ref> ===Inorganic materials=== [[Sulfur hexafluoride]] is an inert, nontoxic insulator that is used in electrical transformers. [[Uranium hexafluoride]] is used in the separation of isotopes of uranium between the [[nuclear fission|fissile]] isotope [[U-235]] and the non-fissile isotope [[U-238]] in preparation of [[nuclear reactor]] [[nuclear fuel|fuel]] and [[atomic bomb]]s. [[Image:100 0783.JPG|thumb|left|PTFE is often used to coat non-stick [[frying pan]]s as it is not water-wettable and possesses high heat resistance.]] ===Fluoropolymers=== [[Fluoropolymers]] such as polytetrafluoroethylene, [[Teflon]], are used as chemically inert and [[biocompatible]] materials for a variety of applications, including as [[prosthesis|surgical implants]] such as [[coronary bypass]] grafts,<ref>{{cite journal |author=Kannan RY, Salacinski HJ, Butler PE, Hamilton G, Seifalian AM |title=Current status of prosthetic bypass grafts: a review |journal=J. Biomed. Mater. Res. Part B Appl. Biomater. |volume=74 |issue=1 |pages=570–81 |year=2005 |pmid=15889440 |doi=10.1002/jbm.b.30247}}</ref> and a replacement for [[soft tissue]] in [[cosmetic surgery|cosmetic]] and [[reconstructive surgery]].<ref>{{cite journal |author=Singh S, Baker JL |title=Use of expanded polytetrafluoroethylene in aesthetic surgery of the face |journal=Clin Plast Surg |volume=27 |issue=4 |pages=579–93 |year=2000 |pmid=11039891}}</ref> These compounds are also commonly used as [[non-stick surface]]s in [[cookware and bakeware]], and the fluoropolymer fabric [[Gore-Tex]] used in breathable garments for outdoor use. ===Cavity-prevention=== {{main|Fluoride therapy}} Fluoride-containing compounds are used in topical and systemic [[fluoride therapy]] for preventing [[Dental caries|tooth decay]]. They are used for [[water fluoridation]] and in many products associated with [[oral hygiene]].<ref name="mcdonagh2000">{{cite journal|author=McDonagh M S, Whiting P F, Wilson P M, Sutton A J, Chestnutt I, Cooper J, Misso K, Bradley M, Treasure E, & Kleijnen J.|date=2000 |title=Systematic review of water fluoridation |journal=[[British Medical Journal]] |volume=321 |issue=7265| pages=855–859|doi=10.1136/bmj.321.7265.855 |pmid=11021861}}</ref> Originally, [[sodium fluoride]] was used to fluoridate water, however, [[hexafluorosilicic acid]] (H<sub>2</sub>SiF<sub>6</sub>) and its salt sodium hexafluorosilicate (Na<sub>2</sub>SiF<sub>6</sub>) are more commonly used additives, especially in the United States. The fluoridation of water prevents tooth decay<ref>{{cite journal |author=Griffin SO, Regnier E, Griffin PM, Huntley V |title=Effectiveness of fluoride in preventing caries in adults |journal=J. Dent. Res. |volume=86 |issue=5 |pages=410–5 |year=2007 |pmid=17452559}}</ref><ref>{{cite journal |author=Winston AE, Bhaskar SN |title=Caries prevention in the 21st century |journal=J Am Dent Assoc |volume=129 |issue=11 |pages=1579–87 |year=1998 |pmid=9818575 |url=http://jada.ada.org/cgi/pmidlookup?view=long&pmid=9818575}}</ref> and is considered by the U.S. [[Centers for Disease Control and Prevention]] as "one of 10 great public health achievements of the 20th century".<ref>[http://www.cdc.gov/fluoridation/]</ref> In some countries where large, centralized water systems are uncommon, fluoride is delivered to the populace by fluoridating table salt. Fluoridation of water is not without critics, however (see [[water fluoridation opposition]]).<ref>{{cite journal |author=Newbrun E |title=The fluoridation war: a scientific dispute or a religious argument? |journal=J Public Health Dent |volume=56 |issue=5 Spec No |pages=246–52 |year=1996 |pmid=9034969 |doi=10.1111/j.1752-7325.1996.tb02447.x}}</ref> [[Image:Halothane2.png|thumb|130px|right|Structure of [[halothane]].]] ===Biomedical applications=== [[Positron emission tomography]] is commonly carried out using fluoride-containing pharmaceuticals such as [[fluorodeoxyglucose]], which is labelled with the [[radioactive isotope]] [[fluorine-18]] that emits [[positron]]s when it decays into <sup>18</sup>O. Fluorine is also part of a large variety of drugs including: [[antipsychotic]]s such as [[fluphenazine]], [[HIV protease inhibitor]]s such as [[tipranavir]], [[antibiotic]]s such as [[ofloxacin]] and [[trovafloxacin]], and [[anesthetic]]s such as [[halothane]].<ref>{{cite journal |author=Park BK, Kitteringham NR, O'Neill PM |title=Metabolism of fluorine-containing drugs |journal=Annu. Rev. Pharmacol. Toxicol. |volume=41 |issue= |pages=443–70 |year=2001 |pmid=11264465 |doi=10.1146/annurev.pharmtox.41.1.443}}</ref> These atoms are incorporated in the drug structures to reduce [[drug metabolism]], as the strong C-F bond resists deactivation in the liver by [[cytochrome P450 oxidase]]s.<ref>{{cite journal |author=Fisher MB, Henne KR, Boer J |title=The complexities inherent in attempts to decrease drug clearance by blocking sites of CYP-mediated metabolism |journal=Curr Opin Drug Discov Devel |volume=9 |issue=1 |pages=101–9 |year=2006 |pmid=16445122}}</ref> ==Toxicology== {{main|fluoride poisoning}} Fluoride-containing compounds are so diverse that it is not possible to generalize on their [[toxicity]], which depends on their reactivity and structure, and in the case of salts, their solubility and ability to release fluoride ions. [[Image:DIF reaction.png|thumb|200px|left|Reaction of the irreversible inhibitor [[diisopropylfluorophosphate]] with a serine protease]] Soluble fluoride salts, of which [[NaF]] is the most common, are mildly toxic but have resulted in both accidental and suicidal deaths from [[Acute toxicity|acute poisoning]].<ref name=Aigueperse/> While the minimum fatal dose in humans is not known, a case of a fatal poisoning of an adult with 4 grams of NaF is documented.<ref name=acute/> [[Sodium fluorosilicate]], Na<sub>2</sub>SiF<sub>6</sub> with its higher fluorine content, can cause death with as little as 0.2 g. The fatal period ranges from 5 min to 12 hours.<ref name=acute/> The mechanism of toxicity involves the combination of the fluoride anion with the calcium ions in the blood to form insoluble [[calcium fluoride]], resulting in [[hypocalcemia]]; calcium is indispensable for the function of the nervous system, and the condition can be fatal. Treatment may involve oral administration of dilute [[calcium hydroxide]] or [[calcium chloride]] to prevent further absorption, and injection of [[calcium gluconate]] to increase the calcium levels in the blood.<ref name=acute>I. M. Rabinowitch. Acute Fluoride Poisoning. ''Can Med Assoc J.'' '''1945''', ''52'', 345–349. [http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=1581810]</ref> [[Hydrogen fluoride]] is more dangerous than salts such as NaF because it is corrosive and volatile, and can result in fatal exposure through inhalation or contact with the skin; calcium gluconate gel is the usual antidote.<ref>Muriale L, Lee E, Genovese J, Trend S. Fatality due to acute fluoride poisoning following dermal contact with hydrofluoric acid in a palynology laboratory. ''Ann Occup Hyg.'' '''1996''' ''40'', 705-710. PMID 8958774.</ref> A few organofluorine compounds are extremely toxic, such as [[organophosphate]]s like [[sarin]] and [[diisopropylfluorophosphate]] that react with the [[cholinesterase enzyme]] at [[neuromuscular junction]]s and thus block the transmission of nerve impulses to the muscles.<ref>{{cite journal |author=Marrs TC |title=Organophosphate poisoning |journal=Pharmacol. Ther. |volume=58 |issue=1 |pages=51–66 |year=1993 |pmid=8415873 |doi=10.1016/0163-7258(93)90066-M}}</ref> Here, a reactive fluorine-phosphorous bond in the inhibitor is the site of nucleophilic attack by a [[serine]] residue in the enzyme's active site, causing the loss of a F<sup>-</sup> ion and [[alkylation]] and inactivation of the enzyme. While PTFE itself is chemically inert and non-toxic, it begins to deteriorate after the temperature of cookware reaches about 500 °F (260 °C), and decompose above 660 °F (350 °C).<ref name=kqat>DuPont, [http://www.teflon.com/Teflon/teflonissafe/keyquestions.html#q3 Key Questions About Teflon®], accessed on 03 Dec 2007.</ref> These degradation products can be lethal to [[bird]]s, and can cause flu-like symptoms in humans.<ref name=kqat/> In comparison, cooking fats, oils, and butter will begin to scorch and smoke at about 392 °F (200 °C), and meat is usually fried between 400&ndash;450 °F (200&ndash;230 °C), but empty cookware can exceed this temperature if left unattended on a hot burner. A 1959 study, (conducted before the [[Food and Drug Administration]] approved the material for use in food processing equipment) showed that the toxicity of fumes given off by the coated pan on dry heating was less than that of fumes given off by ordinary cooking oils.<ref>{{cite web |url=http://www.fda.gov/bbs/topics/CONSUMER/CON00036.html |title=Is That Newfangled Cookware Safe? |publisher=Food and Drug Administration |author=Dale Blumenthal |accessdate=2006-05-20 }}</ref> ==See also== *[[Dental fluorosis]] *[[Fluoride therapy]] *[[Fluoride deficiency]] *[[Halide]] *[[PTFE]] ==References== {{reflist|2}} [[Category:Fluorides| ]] [[Category:Anions]] [[ar:فلوريد]] [[zh-min-nan:Khí-kho ê hu̍t-hoà-bu̍t]] [[cs:Fluoridy]] [[de:Fluoride]] [[et:Fluoriidid]] [[es:Fluoruro]] [[fr:Ion fluorure]] [[it:Fluoruro]] [[he:פלואוריד]] [[nl:Fluoride]] [[ja:フッ化物]] [[pl:Fluorki]] [[pt:Fluoreto]] [[ru:Фторид]] [[fi:Fluoridi]] [[sv:Fluorid]] [[ta:தனிமங்களின் தமிழ்ப் பெயர்கள்]] [[zh:氟化物]]