Sodium monofluorophosphate

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Sodium monofluorophosphate , commonly abbreviated MFP , is an inorganic compound with the chemical formula Na ₂ PO ₃ F. Typical for salt , MFP is odorless, colorless, and soluble in water. This salt is the ingredient in some toothpaste.

Video Sodium monofluorophosphate

Usage

MFP is best known as an ingredient in some toothpastes. It serves as a source of fluoride by the following hydrolysis reaction:

PO ₃ F ^{2 -} OH ^- -> HPO ₄ ^{2 -} F ^-

Fluoride protects the tooth enamel from bacterial attacks that cause dental caries (cavities). Although developed by a chemist at Procter and Gamble, its use in toothpaste (Colgate and Ultra Brite toothpaste) is patented by Colgate-Palmolive, as Procter and Gamble is involved in the marketing of Crest toothpaste (containing stannous fluoride, marketed as "Fluoristan"). In the early 1980s, Crest was reformulated to use the MFP, under the trademark "Fluoristat"; Currently Crest toothpaste uses sodium fluoride or stannous fluoride. Compared with straight fluoride, sodium monofluorophosphate has slightly less aftertaste.

MFP is also used in some medications for the treatment of osteoporosis.

In 1991, sodium monofluorophosphate was discovered by Calgon to inhibit lead dissolution in drinking water when used in concentrations between 0.1 mg/L and 500 mg/L.

Maps Sodium monofluorophosphate

Tooth decay

Tooth decay is caused by bacteria that naturally exist in a person's mouth. These bacteria form a sticky and colorless soft film on teeth called plaque. When foods containing carbohydrates (starches and sugars) are eaten, the bacteria that make up plaque use sugar as a form of energy. They also turn it into glue-like substances that help them stick to the tooth surface. Plaque produces acid, which attacks the enamel.

Chemical decay

Enamel teeth consist mostly of calcium hydroxyphosphate, Ca ₅ (PO ₄ ) ₃ OH, also known as mineral hydroxyapatite. Apatite is a hard and insoluble compound. Acid (H ), produced especially after eating high sugar, attacks apatite:

Ca ₅ (PO ₄ ) ₃ OH _(s) H _(aq) -> Ca ₅ (PO ₄ ) _{3 (aq)} H ₂ O _(l)

enamel fluoridation chemistry

Apatite degradation by loss of OH ^- causes the enamel to dissolve. This process is reversible because the supply of saliva returns OH ^- to reform apatite. If fluoride, F ^- , the ions present in saliva, fluorapatite, Ca ₅ (PO ₄ ) ₃ F , also form. _{4 3 (aq) 4} F _(s)

Fluorapatite rejects attacks by acid better than the apatite itself, so dental enamel rejects decay better than enamel that does not contain fluoride.

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Preparation and structure

Sodium monofluorophosphate is produced industrially by sodium fluoride reaction with sodium metaphosphate:

NaPO ₃ NaF -> Na ₂ PO ₃ F

This process involves cutting a pyrophosphate bond, analogous to hydrolysis. NaMFP can also be prepared by treating tetracodium pyrophosphate or disodium phosphate with hydrogen fluoride.

In the laboratory, MFP can be prepared by hydrolysis of difluorophosphoric ions with dilute sodium hydroxide:

PO ₂ F ₂ ^- 2 NaOH -> Na ₂ PO ₃ FH ₂ OF ^-

Structure

The fluorophosphoric anion structure consists of phosphorus in the center of a tetrahedron determined by three oxygen atoms and one fluorine. The formal representation describes the double bond between an oxygen atom and a phosphor, with a single bond for two other oxygen atoms and fluorine. In this very formal depiction, the negative charge is localized to the O atom of a single P-O bond. MFP is similar to and isoelectronic with Na ₂ SO ₄ . Anion has symmetry C _3v .

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Discovery and development

Sodium monofluorophosphate was first described in 1929 by the German chemist Willy Lange, who was with the University of Berlin. The unsuccessful effort to prepare free monofluorophosphoric acid led him to check the stability of his ester. Together with Gerda von KrÃÆ'¼ger, one of his disciples, Lange thus synthesized diethyl fluorophosphate and several analogues, which proved to be quite toxic, associated with neural agents. In the 1930s, Gerhard Schrader, working for the German company IG Farben, tried to develop a synthetic insecticide. His work focuses on phosphoric acid esters and results in the unintentional discovery of several other neurological agents such as DFP (Diisopropyl fluorophosphate), Tabun, Soman, and Sarin. Meanwhile, Lange, who married a Jewish woman, emigrated from Germany to the United States and started working for Procter and Gamble Company. In 1947, he and Ralph Livingston of Monsanto Company published a free preparation of fluorophosphoric acid and cited the use of some toxic esters of monofluorophosphoric acid (such as DFP) in the treatment of glaucoma and myasthenia gravis. The well known toxicity of these esters causes concerns that simple salts may also be toxic, and such fears prevent large-scale commercial use of the salts. In 1950, under the sponsorship of the compound manufacturer, Ozark Chemical Company, the toxicity of sodium monofluorophosphate was studied by Harold Hodge at the University of Rochester which included anti-cavity testing. In 1967 Colgate-Palmolive filed several patents on the use of sodium monofluorophosphate in toothpaste.

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Security

The usual MFP content in toothpaste is 0.76%. This compound is used as a substitute for sodium fluoride, especially in children's toothpaste, since it is less toxic, although both have moderate toxicity. LD ₅₀ in rats is 0.9 g/kg. Salt exhibits limited musculoskeletal toxicity and breathing.

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References

Source of the article : Wikipedia