Fluoride

Published on February 2017 | Categories: Documents | Downloads: 53 | Comments: 0 | Views: 529
of 9
Download PDF   Embed   Report

Comments

Content

Fluoride From Wikipedia, the free encyclopedia Fluoride Systematic name[hide]

Fluoride[1] Identifiers CAS number PubChem ChemSpider KEGG C00742 MeSH Fluoride ChEBI CHEBI:17051 ChEMBL CHEMBL1362 14905 16984-48-8 28179 26214

Gmelin Reference Jmol-3D images Image 1 SMILES [show] InChI [show] Properties Molecular formula Molar mass Exact mass

F−

18.9984032 g mol-1 18.998403205 g mol-1

Thermochemistry Standard molar

entropy So298 145.58 J K-1 mol-1 Related compounds Other anions Bromide

Chloride Iodide Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) Infobox references

Fluoride is the anion F−, the reduced form of fluorine when as an ion and when bonded to another element. Both organofluorine compounds and inorganic fluorine containing compounds are called fluorides.*2+ Fluoride, like other halides, is a monovalent ion (−1 charge). Its compounds often have properties that are distinct relative to other halides. Structurally, and to some extent chemically, the fluoride ion resembles the hydroxide ion. Fluorine-containing compounds range from potent toxins such as sarin to life-saving pharmaceuticals such as efavirenz, and from inert materials such as carbon tetrafluoride to the highly reactive sulfur tetrafluoride. The range of fluorine-containing compounds is vast because fluorine is capable of forming compounds with all the elements except helium and neon.[3][4]Contents [hide] 1 Occurrence 1.1 Natural occurrence 2 Applications 2.1 Pesticides 2.2 Organic synthesis 2.3 Inorganic fluorides 2.4 Fluoropolymers 2.5 Cavity prevention 2.6 Biomedical applications 3 Toxicology

4 See also 5 References 6 External links

[edit] Occurrence

The mineral fluorite, a common mineral and chief source of fluoride for commercial applications.[5][6]

Solutions of inorganic fluorides in water contain F− and bifluoride HF2−.*7+ 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 (UF6). 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. [edit] Natural occurrence

Many fluoride minerals are known, but of paramount commercial importance are fluorite and fluorapatite.[5] Fluoride is found naturally in low concentration in drinking water and foods. Waters from underground sources are more likely to have higher levels of fluoride, whereas the concentration in seawater averages 1.3 parts per million (ppm).[8] Fresh water supplies generally contain between 0.01–0.3 ppm, whereas the ocean contains between 1.2 and 1.5 ppm.[9] [edit] Applications

Fluorides are pervasive in modern technology. Hydrofluoric acid is the fluoride synthesized on the largest scale. It is produced by treating fluoride minerals with sulfuric acid. Hydrofluoric acid and its anhydrous form hydrogen fluoride are used in the production of fluorocarbons and aluminium fluorides. Hydrofluoric acid has a variety of specialized applications, including its ability to dissolve glass.[5]

[edit] Pesticides

Sulfuryl fluoride is used as a pesticide and fumigant on agricultural crops. In 2010, the United States Environmental Protection Agency proposed to withdraw the use of sulfuryl fluoride on food. Sulfuryl fluoride releases fluoride when metabolized.[10][11] Cryolite is a pesticide that can leave fluoride on agricultural commodities.[12][13] [edit] Organic synthesis

Fluoride reagents are significant in synthetic organic chemistry. Due to the affinity of silicon for fluoride, and the ability of silicon to expand its coordination number, silyl ether protecting groups can be easily removed by the fluoride sources such as sodium fluoride and tetra-n-butylammonium fluoride (TBAF). [edit] Inorganic fluorides

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 fissile isotope U-235 and the non-fissile isotope U-238 in preparation of nuclear reactor fuel and atomic bombs. The volatility of fluorides of uranium and other elements may also be used for nuclear fuel reprocessing.

PTFE is often used to coat non-stick frying pans as it is not water-wettable and possesses high heat resistance. [edit] Fluoropolymers

Fluoropolymers such as polytetrafluoroethylene, Teflon, are used as chemically inert and biocompatible materials for a variety of applications, including as surgical implants such as coronary bypass grafts,[14] and a replacement for soft tissue in cosmetic and reconstructive surgery.[15] These compounds are also commonly used as non-stick surfaces in cookware and bakeware, and the fluoropolymer fabric Gore-Tex used in breathable garments for outdoor use.

[edit] Cavity prevention Main articles: fluoride therapy and water fluoridation

Fluoride-containing compounds are used in topical and systemic fluoride therapy for preventing tooth decay. They are used for water fluoridation and in many products associated with oral hygiene.[16] Originally, sodium fluoride was used to fluoridate water; hexafluorosilicic acid (H2SiF6) and its salt sodium hexafluorosilicate (Na2SiF6) are more commonly used additives, especially in the United States. The fluoridation of water is known to prevent tooth decay[17][18] 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".[19][20] In some countries where large, centralized water systems are uncommon, fluoride is delivered to the populace by fluoridating table salt. Fluoridation of water has its critics (see Water fluoridation controversy).[21]

Structure of halothane. [edit] 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, which emits positrons when it decays into 18O.

Numerous drugs contain fluorine including antipsychotics such as fluphenazine, HIV protease inhibitors such as tipranavir, antibiotics such as ofloxacin and trovafloxacin, and anesthetics such as halothane.[22] Fluorine is incorporated in the drug structures to reduce drug metabolism, as the strong C-F bond resists deactivation in the liver by cytochrome P450 oxidases.[23]

Fluoride salts are commonly used to inhibit the activity of phosphatases, such as serine/threonine phosphatases.[24] Fluoride mimics the nucleophilic hydroxyl ion in these enzymes' active sites.[25] 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.[26][27]

[edit] Toxicology Main article: Fluoride poisoning

Reaction of the irreversible inhibitor diisopropylfluorophosphate with a serine protease

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.

Soluble fluoride salts, of which sodium fluoride is the most common, are mildly toxic but have resulted in both accidental and suicidal deaths from acute poisoning.[5] While the minimum fatal dose in humans is not known, the lethal dose for most adult humans is estimated at 5 to 10 g (which is equivalent to 32 to 64 mg/kg elemental fluoride/kg body weight).[28][29][30] However, a case of a fatal poisoning of an adult with 4 grams of sodium fluoride is documented,[31] while a dose of 120 g sodium fluoride has been survived.[32] A toxic dose that may lead to adverse health effects is estimated at 3 to 5 mg/kg of elemental fluoride.[33] For Sodium fluorosilicate (Na2SiF6), the median lethal dose (LD50) orally in rats is 0.125 g/kg, corresponding to 12.5 g for a 100 kg adult.[34] The fatal period ranges from 5 min to 12 hours.[31] 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.[31] 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 upon contact with the skin; calcium gluconate gel is the usual antidote.[35]

In the higher doses used to treat osteoporosis, sodium fluoride can cause pain in the legs and incomplete stress fractures when the doses are too high; it also irritates the stomach, sometimes so severely as to cause ulcers. Slow-release and enteric-coated versions of sodium fluoride do not have gastric side effects in any significant way, and have milder and less frequent complications in the bones.[36] In the lower doses used for water fluoridation, the only clear adverse effect is dental fluorosis, which can alter the appearance of children's teeth during tooth development; this is mostly mild and is unlikely to represent any real effect on aesthetic appearance or on public health.[37] 10 – Chlorine

The chlorination of water is a disinfecting method used by water treatment plants to eliminate the presence of bacteria and other microorganisms in city supplies. This seems beneficial, but consider the consequences: chlorine in water often reacts with other naturally-occurring elements to produce toxins that are carcinogenic. Prolonged exposure has been linked with several adverse health conditions like asthma and several types of cancer.

#9 – Lead

According to the Centers for Disease Control, Lead in water is a major concern for children and pregnant women, as it affects physical and mental development. Although measures taken over the last few decades have drastically reduced the amount of lead in water supplies, it is still often found in houses and buildings with old pipes. Water that sits for long periods of time in corroded pipes can become contaminated and, when drank, result in lead poisoning.

#8 – Cysts

Cryptosporidium and Giardia are two of the most common water-borne microbiological cysts. These protozoan parasites enter lakes and streams through sewage and animal waste. Drinking water from said lakes and streams is not such a good idea, unless you’re sure the cysts have been filtered out. You could end up with a mild to severe gastrointestinal illness.

#7 – BPA

BPA, otherwise known as bisphenol-A, is found in the plastic used in water bottles and other manufactured products. A large number of studies on BPA have found its effects on the body to be toxic. If BPA leaches into bottled water, it could result in many different types of cancer.

#6 – Fluoride

Ah, the Fluoride debate: to fluoridate or not to fluoridate. Well, some maintain that fluoride in water is beneficial to dental health. Others claim it is linked to bone cancer and can actually cause dental fluorosis with extensive exposure. It’s all a matter of where your priorities lie. Sure you might die of cancer, but at least you can still flash those healthy, strong pearly whites during your funeral visitation, right?

#5 – Fecal Coliforms

Yes, you read that right. While bottled water companies market their product as healthier than tap, many bottles have been found to contain a small percentage of feces. What’s another word for feces?

You don’t want that in your water.

#4 – Pesticides and Herbicides

This might not sound like such a big deal, since pesticides and herbicides are regularly used to farm our world’s food supplies. But whether you eat them or drink them, these substances are toxic, and have been labeled “gender benders.” Studies have found that atrazine, a common herbicide, is able to turn male frogs into female frogs. Farm run-off puts these toxins in our water supplies, so unless you’re trying to induce a sex change, I’d be careful.

#3 – Pharmaceuticals

Pharmaceuticals are scary, because they may be harder to filter than all of these other substances. Since pharmaceuticals do not biodegrade, throwing them in the trash or flushing them down the toilet may cause them to end up in your water supply. Ninety percent of pills can pass through humans unchanged, so that human waste becomes a factor as well. Repeatedly ingesting water contaminated with pharmaceuticals can disrupt normal hormone function or lead to cancer.

#2 – Natural Gas

Several homes across the country, all of which are near a local natural-gas drilling site, have witnessed the miracle of flaming tap water. The good news is that it’s easy to test for – hold a lighter up to your faucet. The down side is that you might get burned while doing so.

#1 – Crickets

In the words of Dr. Peter Gleick, “yes, crickets.” Gleick recently published a book called, Bottled and Sold: The Story Behind Our Obsession With Bottled Water. In it, he discusses the contaminants found in bottled water that most people don’t look for. His examples include a 1994 recall on a Texasmanufactured, bottled, sparkling water that was found to be contaminated with crickets.

I don’t think it gets more disturbing than this, but I could be wrong. Are these the ten worst things found in tap and bottled water supplies? Perhaps you have some contaminated water stories you’d like to share.

Sponsor Documents

Or use your account on DocShare.tips

Hide

Forgot your password?

Or register your new account on DocShare.tips

Hide

Lost your password? Please enter your email address. You will receive a link to create a new password.

Back to log-in

Close