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| Names | |
|---|---|
| IUPAC name Disodium phosphorofluoridate | |
| Other names Sodium fluorophosphate, disodium monofluorophosphate | |
| Identifiers | |
3D model (JSmol) | |
| ChEBI | |
| ChEMBL | |
| ChemSpider |
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| ECHA InfoCard | 100.030.381 |
| EC Number |
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| RTECS number |
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| UNII | |
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| Properties | |
| Na2PFO3 | |
| Molar mass | 143.95 g/mol |
| Appearance | white powder |
| Melting point | 625 °C (1,157 °F; 898 K) |
| 25 g/100 mL | |
| Solubility | insoluble inethanol,ether |
| Pharmacology | |
| A01AA02 (WHO) A12CD02 (WHO) | |
| Hazards | |
| NFPA 704 (fire diamond) | |
| Flash point | Non-flammable |
| Lethal dose or concentration (LD, LC): | |
LD50 (median dose) | 0,9g/kg (rat, oral)[1] |
| Safety data sheet (SDS) | Sigma-Aldrich |
Except where otherwise noted, data are given for materials in theirstandard state (at 25 °C [77 °F], 100 kPa). | |
Sodium monofluorophosphate, commonly abbreviatedSMFP, is aninorganicfluorophosphate with thechemical formula Na2PO3F. Typical for asalt, SMFP is odourless, colourless, and water-soluble. This salt is an ingredient in sometoothpastes.[2]
SMFP is best known as an ingredient in sometoothpastes.[3] It functions as a source offluoride via the followinghydrolysis reaction:[2]
Fluoride protects tooth enamel from attack by bacteria that causedental caries (cavities). Although developed by a chemist atProcter and Gamble, its use in toothpaste (Colgate toothpaste andUltra Brite) was patented byColgate-Palmolive, as Procter and Gamble was engaged in the marketing ofCrest toothpaste (containingstannous fluoride, marketed as "Fluoristan"). In the early 1980s, Crest was reformulated to use SMFP, under the trademark "Fluoristat"; today Crest toothpastes usesodium fluoride orstannous fluoride. Compared to straight fluorides, sodium monofluorophosphate has slightly less aftertaste.
SMFP is also used in some medications for the treatment ofosteoporosis.[2]
In 1991, sodium monofluorophosphate was found byCalgon to inhibit the dissolution oflead in drinking water when used in concentrations between 0.1 mg/L and 500 mg/L.[4]
Tooth decay is caused by bacteria naturally present in one's mouth. These bacteria form a sticky, colorless soft film on the teeth calledplaque. When foods containingcarbohydrates (starches andsugars) are eaten, the bacteria that form plaque use the sugar as a form of energy. They also turn it into a glue-like substance that helps them stick to the surface of the tooth. The plaque producesacid, which attacks theenamel.[5]
Tooth enamel consists mostly of calcium hydroxyphosphate, Ca5(PO4)3OH, also known as the mineralhydroxyapatite. Apatite is a hard, insoluble compound. Acid (H+), produced especially after a high-sugar meal, attacks the apatite:
The degradation of apatite by loss of OH− causes the enamel to dissolve. The process is reversible as saliva supplies back OH− to reform apatite. If fluoride, F−, ions are present in saliva,fluorapatite, Ca5(PO4)3F, also forms.
Fluorapatite resists attacks by acids better than apatite itself, so the tooth enamel resists decay better than enamel containing no fluoride.[6]
Sodium monofluorophosphate is produced industrially by the reaction of sodium fluoride with sodiummetaphosphate:[2]
The process involves scission of a pyrophosphate bond, analogous to hydrolysis. SMFP can also be prepared by treatingtetrasodium pyrophosphate ordisodium phosphate with hydrogen fluoride.[2]
In the laboratory, SMFP can be prepared byhydrolysis of difluorophosphate ions with dilutesodium hydroxide:
The structure of the fluorophosphate anion consists ofphosphorus at the center of a tetrahedron defined by threeoxygen atoms and onefluorine. Formal representations depict a double bond between one oxygen atom and phosphorus, with single bonds for the other two oxygen atoms and the fluorine. In this very formal depiction, negative charge is localized on the O atoms of the single P-O bonds. SMFP isisoelectronic withsodium sulfate. The anion has C3vsymmetry.
Sodium monofluorophosphate was first described in 1929 by the German chemistWilly Lange, who was then with the University of Berlin. His fruitless attempts to prepare freemonofluorophosphoric acid led him to look at the acid'sesters. Together withGerda von Krüger, one of his students, Lange thus synthesizeddiethyl fluorophosphate which proved to be quite toxic, being the first evernerve agent. In the 1930s,Gerhard Schrader, working for the German companyIG Farben, tried to develop syntheticinsecticide. His work focused on esters of phosphoric acids and resulted in the discovery ofIsoflurophate,Tabun,Soman, andSarin. In the meantime, Lange, who was married to a Jewish woman, emigrated from Germany to the United States and started work forProcter and Gamble Company. In 1947, he and Ralph Livingston ofMonsanto Company published the preparation of the free fluorophosphoric acids and mentioned the use ofisoflurophate in the treatment ofglaucoma andmyasthenia gravis. The well known toxicity of these esters led to fears that the simple salts might also be toxic, and such fears precluded any large scale commercial use of the salts. In 1950, under sponsorship of the manufacturer of the compounds,Ozark Chemical Company, the toxicity of sodium monofluorophosphate was studied byHarold Hodge at theUniversity of Rochester who included anti-cavity testing. In 1967Colgate-Palmolive filed several patents on the use of sodium monofluorophosphate in toothpaste.[4]
The usual content of SMFP in toothpaste is 0.76%. The compound is used in place of sodium fluoride, particularly in children's toothpastes, because it is less acutely toxic, although both have modest toxicities. TheLD50 in rats is 0.9 g/kg.[7]
