Sodium perborate is

chemical compound A chemical compound is a chemical substance composed of many identical molecules (or molecular entities) containing atoms from more than one chemical element held together by chemical bonds. A molecule consisting of atoms of only one ele ...

whose

chemical formula In chemistry, a chemical formula is a way of presenting information about the chemical proportions of atoms that constitute a particular chemical compound or molecule, using chemical element symbols, numbers, and sometimes also other symbols, ...

may be written , , or, more properly, ·. Its name is sometimes abbreviated as PBS (not to be confused with phosphate-buffered saline). The compound is commonly encountered in anhydrous form or as a hexahydrate (commonly called "monohydrate" or PBS-1 and "tetrahydrate" or PBS-4, after the early assumption that would be the anhydrous form).Alexander McKillop and William R Sanderson (1995): "Sodium perborate and sodium percarbonate: Cheap, safe and versatile oxidising agents for organic synthesis". ''Tetrahedron'', volume 51, issue 22, pages 6145-6166. They are both white, odorless, water-soluble solids.B.J. Brotherton "Boron: Inorganic Chemistry" in ''Encyclopedia of Inorganic Chemistry'' (1994) Ed. R. Bruce King, John Wiley & Sons This salt is widely used in laundry detergents, as one of the peroxide-based bleaches.

Structure

Unlike

sodium percarbonate Sodium percarbonate is a chemical substance with formula . It is an adduct of sodium carbonate ("soda ash" or "washing soda") and hydrogen peroxide (that is, a perhydrate) whose formula is more properly written as 2 · 3 . I ...

and

sodium perphosphate Sodium is a chemical element with the symbol Na (from Latin ''natrium'') and atomic number 11. It is a soft, silvery-white, highly reactive metal. Sodium is an alkali metal, being in group 1 of the periodic table. Its only stable isot ...

, the compound is not simply an

adduct An adduct (from the Latin ''adductus'', "drawn toward" alternatively, a contraction of "addition product") is a product of a direct addition of two or more distinct molecules, resulting in a single reaction product containing all atoms of all co ...

with hydrogen peroxide. Rather, it contains a perborate

anion An ion () is an atom or molecule with a net electrical charge. The charge of an electron is considered to be negative by convention and this charge is equal and opposite to the charge of a proton, which is considered to be positive by conve ...

consisting of a cyclic –B–O–O–B–O–O– core with two

hydroxy group In chemistry, a hydroxy or hydroxyl group is a functional group with the chemical formula and composed of one oxygen atom covalently bonded to one hydrogen atom. In organic chemistry, alcohols and carboxylic acids contain one or more hydrox ...

s attached to each boron atom. The ring adopts a chair conformation.

Hydrates

The compound also crystallizes from water as the hexahydrate, ·6, that is, or . The anhydrous compound is commonly but incorrectly called a "monohydrate" after the original formulation · instead of the correct . Likewise, the hexahydrate is usually called "tetrahydrate" and formulated as ·4. Both forms are white, odorless, water-soluble solids.B.J. Brotherton "Boron: Inorganic Chemistry" in ''Encyclopedia of Inorganic Chemistry'' (1994) Ed. R. Bruce King, John Wiley & Sons The "monohydrate" and the "tetrahydrate" are the commercially important forms.

Chemistry

Sodium perborate undergoes

hydrolysis Hydrolysis (; ) is any chemical reaction in which a molecule of water breaks one or more chemical bonds. The term is used broadly for substitution, elimination, and solvation reactions in which water is the nucleophile. Biological hydrolysis ...

in contact with water, producing

hydrogen peroxide Hydrogen peroxide is a chemical compound with the formula . In its pure form, it is a very pale blue liquid that is slightly more viscous than water. It is used as an oxidizer, bleaching agent, and antiseptic, usually as a dilute solution (3% ...

and borate. More precisely, in solution the cyclic anion hydrolizes into two anions , which then enter in equilibrium with

boric acid Boric acid, more specifically orthoboric acid, is a compound of boron, oxygen, and hydrogen with formula . It may also be called hydrogen borate or boracic acid. It is usually encountered as colorless crystals or a white powder, that dissolve ...

, hydrogen peroxide , the

hydroperoxyl The hydroperoxyl radical Radical may refer to: Politics and ideology Politics *Radical politics, the political intent of fundamental societal change *Radicalism (historical), the Radical Movement that began in late 18th century Britain and sprea ...

anion , and the tetrahydroxyborate anion : : + 2 H2O <=> 2 (OH)3(OOH) : (OH)3(OOH) <=> B(OH)3 + HOO- :B(OH)3 + HOO- + H2O <=> (OH)4 + H2O2 As the concentration of the solution increases, other peroxoborate species become significant. With excess , the anions , , and eventually appear. At high borate concentrations, the sodium perborate with dimeric anion crystallizes out, due to its relatively low solubility. The monohydrate form dissolves better than the tetrahydrate and has higher heat stability; it is prepared by heating the tetrahydrate.

Preparation

Sodium perborate is manufactured by reaction of

borax Borax is a salt (chemistry), salt (ionic compound), a hydration (chemistry), hydrated borate of sodium, with chemical formula often written . It is a colorless crystalline solid, that dissolves in water to make a base (chemistry), basic aqueo ...

and

sodium hydroxide Sodium hydroxide, also known as lye and caustic soda, is an inorganic compound with the formula NaOH. It is a white solid ionic compound consisting of sodium cations and hydroxide anions . Sodium hydroxide is a highly caustic base and alkal ...

to give sodium metaborate , which is then reacted with hydrogen peroxide to give hydrated sodium perborate: :Na2B4O7 + 2NaOH -> 4 NaBO2 + H2O : 2NaBO2 + 2H2O2 -> Na2B2O4(OH)4 A

surfactant Surfactants are chemical compounds that decrease the surface tension between two liquids, between a gas and a liquid, or interfacial tension between a liquid and a solid. Surfactants may act as detergents, wetting agents, emulsifiers, fo ...

may be added to control crystal size.J. Dugua and B.Simon (1978): "Crystallization of sodium perborate from aqueous solutions: I. Nucleation rates in pure solution and in presence of a surfactant". ''Journal of Crystal Growth'', volume 44, issue 3, pages 265-279.J. Dugua and B.Simon (1978): "Crystallization of sodium perborate from aqueous solutions: II. Growth kinetics of different faces in pure solution and in the presence of a surfactant". ''Journal of Crystal Growth'', volume 44, issue 3, pages 280-286. It may also be produced in the electrolysis of an aqueous solution of a solution containing borax, sodium carbonate and sodium bicarbonate (potassium dichromate is added to improve yield along with sodium silicate). A copper pipe is used as a cathode and platinum for the anode, the current being 6 amperes at 7 to 8 volts, and the temperature 10°C.

Uses

Sodium perborate serves as a stable source of active oxygen in many

detergent A detergent is a surfactant or a mixture of surfactants with cleansing properties when in dilute solutions. There are a large variety of detergents, a common family being the alkylbenzene sulfonates, which are soap-like compounds that are m ...

s, laundry detergents, cleaning products, and laundry bleaches. It is a less aggressive bleach than sodium hypochlorite and other chlorine-based bleaches, causing less degradation to dyes and

textile Textile is an umbrella term that includes various fiber-based materials, including fibers, yarns, filaments, threads, different fabric types, etc. At first, the word "textiles" only referred to woven fabrics. However, weaving is not t ...

s. 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), one must mix it with a suitable activator, typically tetraacetylethylenediamine (TAED). Sodium perborate is also present in some tooth bleaching formulas for non vital root treated teeth. The compound is inserted in the root canal 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. However, this use has been banned in the

European Union The European Union (EU) is a supranational political and economic union of member states that are located primarily in Europe. The union has a total area of and an estimated total population of about 447million. The EU has often been ...

. The compound has

antiseptic An antiseptic (from Greek ἀντί ''anti'', "against" and σηπτικός ''sēptikos'', "putrefactive") is an antimicrobial substance or compound that is applied to living tissue/skin to reduce the possibility of infection, sepsis, or putre ...

properties and can act as a

disinfectant A disinfectant is a chemical substance or compound used to inactivate or destroy microorganisms on inert surfaces. Disinfection does not necessarily kill all microorganisms, especially resistant bacterial spores; it is less effective than s ...

. It is also used as a "disappearing"

preservative A preservative is a substance or a chemical that is added to products such as food products, beverages, pharmaceutical drugs, paints, biological samples, cosmetics, wood, and many other products to prevent decomposition by microbial growth or ...

in some brands of

eye drop Eye drops or eyedrops are liquid drops applied directly to the surface of the eye usually in small amounts such as a single drop or a few drops. Eye drops usually contain saline to match the salinity of the eye. Drops containing only saline an ...

s. Sodium perborate is also used as an

oxidizing Redox (reduction–oxidation, , ) is a type of chemical reaction in which the oxidation states of substrate change. Oxidation is the loss of electrons or an increase in the oxidation state, while reduction is the gain of electrons or a d ...

reagent in

organic synthesis Organic synthesis is a special branch of chemical synthesis and is concerned with the intentional construction of organic compounds. Organic molecules are often more complex than inorganic compounds, and their synthesis has developed into one o ...

. For example, it converts

thioether In organic chemistry, an organic sulfide (British English sulphide) or thioether is an organosulfur functional group with the connectivity as shown on right. Like many other sulfur-containing compounds, volatile sulfides have foul odors. A sul ...

s into

sulfoxide In organic chemistry, a sulfoxide, also called a sulphoxide, is an organosulfur compound containing a sulfinyl () functional group attached to two carbon atoms. It is a polar functional group. Sulfoxides are oxidized derivatives of sulfides. E ...

s and sulfones.

Safety

In the

, sodium perborate, like most borates, was classified as "carcinogenic, mutagenic, or toxic for reproduction" (CMR), category 1B of Regulation (EC) 790/2009, as a result of being included in Part 3 of Annex VI of the regulation 1272/2008 on Classification, Labelling and Packaging (CLP) of substances and mixtures. As a result, their use has been automatically banned in cosmetic products in the EU, in any concentration, starting 1 December 2010. That extends to the use of perborates for tooth whitening.Nature Inc. (2015): "Chemical used in beauty salon teeth whitening banned by EU". ''BDJ Team'', volume 2, article 15075, 26 June 2015.

References

https://patents.google.com/patent/US3038842A/en

External links

Borax Detergent Book: Bleaching

Sodium perborate history, image

Sodium perborate in organic synthesis
{{Borates Sodium compounds Borates Peroxides Cleaning product components Antiseptics Bleaches Oxidizing agents