Sodium perborate

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Sodium perborate
Perborate dimer, peroxide bond shown in red, charges in blue
Names
Other names
PBS-1 (mono), PBS-4 (tetra)
Identifiers
3D model (JSmol)
ChEBI
ChemSpider
ECHA InfoCard 100.106.721
EC Number 231-556-4
RTECS number SC7350000
UNII
UN number 1479
Properties
NaBO3·nH2O
Molar mass 99.815 g/mol (monohydrate);
153.86 g/mol (tetrahydrate)
Appearance white powder
Odor odorless
Melting point 63 °C (145 °F; 336 K) (tetrahydrate)
Boiling point 130 to 150 °C (266 to 302 °F; 403 to 423 K) (tetrahydrate, decomposes)
2.15 g/100 mL (tetrahydrate, 18 °C)
Pharmacology
A01AB19 (WHO)
Hazards
Safety data sheet ICSC 1046
NFPA 704
Flammability code 1: Must be pre-heated before ignition can occur. Flash point over 93 °C (200 °F). E.g., canola oil Health code 1: Exposure would cause irritation but only minor residual injury. E.g., turpentine Reactivity code 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g., liquid nitrogen Special hazards (white): no codeNFPA 704 four-colored diamond
Flash point non-flammable
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

Sodium perborate (PBS) is a white, odorless, water-soluble chemical compound with the chemical formula Na2B2O4(OH)4. It is usually encountered as the tetrahydrate, but monohydrate, NaBO3·H2O and trihydrates are well known NaBO3·3H2O and[1] The monohydrate and tetrahydrate are the commercially important forms.[1] This salt is widely used in laundry detergents.

Preparation and reactions[edit]

Sodium perborate is manufactured by reaction of disodium tetraborate pentahydrate, hydrogen peroxide, and sodium hydroxide.[1] The monohydrate form dissolves better than the tetrahydrate and has higher heat stability; it is prepared by heating the tetrahydrate. Sodium perborate undergoes hydrolysis in contact with water, producing hydrogen peroxide and borate.[1]

The salt is a reagent in organic synthesis. It converts thioethers into sulfoxides and sulfones for example.[2]

Structure[edit]

Unlike sodium percarbonate and perphosphate, the sodium perborate is not simply an adduct with hydrogen peroxide.[3] Rather, it adopts a cyclic structure with a B2O4 core and four hydroxide groups attached to the two boron atoms. The ring has a chair-shaped 6-membered ring.[4]

Uses[edit]

It serves as a source of active oxygen in many detergents, laundry detergents, cleaning products, and laundry bleaches.[1] It is also present in some tooth bleaching formulas. It is used as a bleaching agent for internal bleaching of a non vital root treated tooth. The sodium perborate is placed inside the tooth and left in place for an extended period of time to allow it to diffuse into the tooth and bleach stains from the inside out. It has antiseptic properties and can act as a disinfectant. It is also used as a "disappearing" preservative in some brands of eye drops.

Sodium perborate is a less aggressive bleach than sodium hypochlorite, causing less degradation to dyes and textiles. Borates also have some non-oxidative bleaching properties.

Sodium perborate releases oxygen rapidly at temperatures over 60 °C. To make it active at lower temperatures (40–60 °C), it has to be mixed with a suitable activator, typically tetraacetylethylenediamine (TAED).

See also[edit]

References[edit]

  1. ^ a b c d e B.J. Brotherton "Boron: Inorganic Chemistry" in Encyclopedia of Inorganic Chemistry (1994) Ed. R. Bruce King, John Wiley & Sons ISBN 0-471-93620-0
  2. ^ McKillop, Alexander; Kabalka, George W.; Reddy, Marepally Srinivasa (2008). "Sodium perborate". e-EROS Encyclopedia of Reagents for Organic Synthesis. doi:10.1002/047084289X. 
  3. ^ Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. ISBN 0-08-037941-9. 
  4. ^ Carrondo, M. A. A. F. de C. T.; Skapski, A. C. (1978). "Refinement of the X-ray crystal structure of the industrial bleaching agent disodium tetrahydroxo-di-μ-peroxo-diborate hexahydrate, Na2[B2(O2)2(OH)4]·6H2O". Acta Crystallogr B. 34: 3551. doi:10.1107/S0567740878011565. 

External links[edit]