A peroxy acid (often spelled as one word, peroxyacid, and sometimes called peracid) is an

acid An acid is a molecule or ion capable of either donating a proton (i.e. Hydron, hydrogen cation, H+), known as a Brønsted–Lowry acid–base theory, Brønsted–Lowry acid, or forming a covalent bond with an electron pair, known as a Lewis ...

which contains an acidic group. The two main classes are those derived from conventional

mineral acid A mineral acid (or inorganic acid) is an acid derived from one or more inorganic compounds, as opposed to organic acids which are acidic, organic compounds. All mineral acids form hydrogen ions and the conjugate base when dissolved in water. Ch ...

s, especially

sulfuric acid Sulfuric acid (American spelling and the preferred IUPAC name) or sulphuric acid (English in the Commonwealth of Nations, Commonwealth spelling), known in antiquity as oil of vitriol, is a mineral acid composed of the elements sulfur, oxygen, ...

, and the peroxy derivatives of organic

carboxylic acid In organic chemistry, a carboxylic acid is an organic acid that contains a carboxyl group () attached to an Substituent, R-group. The general formula of a carboxylic acid is often written as or , sometimes as with R referring to an organyl ...

s. They are generally strong

oxidizer An oxidizing agent (also known as an oxidant, oxidizer, electron recipient, or electron acceptor) is a substance in a redox chemical reaction that gains or " accepts"/"receives" an electron from a (called the , , or ''electron donor''). In ot ...

Inorganic peroxy acids

Peroxymonosulfuric acid Peroxymonosulfuric acid, also known as persulfuric acid, peroxysulfuric acid is the inorganic compound with the formula . It is a white solid. It is a component of Caro's acid, which is a solution of peroxymonosulfuric acid in sulfuric acid cont ...

(Caro's acid) is probably the most important inorganic peracid, at least in terms of its production scale. It is used for the bleaching of pulp and for the detoxification of cyanide in the mining industry. It is produced by treating sulfuric acid with

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 viscosity, viscous than Properties of water, water. It is used as an oxidizer, bleaching agent, and antiseptic, usua ...

. Peroxymonophosphoric acid () is prepared similarly. Some peroxy acids are only hypothetical, but their anions are known. This is the case for peroxycarbonate and perborate (see

sodium perborate Sodium perborate are chemical compounds with chemical formula (H2O)x. Commonly encountered salts are the anhydrous form (x = 0) and as a hydrate, hexahydrate (x = 6). These two species are sometimes called, respectively, "monohydrate" or PBS-1 a ...

Organic peracids

Production

Several organic peroxyacids are commercially useful. They can be prepared in several ways. Most commonly, peracids are generated by treating the corresponding

with hydrogen peroxide: : A related reaction involves treatment of the carboxylic anhydride: : This method is popular for converting cyclic anhydrides to the corresponding monoperoxyacids, for example monoperoxyphthalic acid. The third method involves treatment of

acid chloride In organic chemistry, an acyl chloride (or acid chloride) is an organic compound with the functional group . Their formula is usually written , where R is a side chain. They are reactive derivatives of carboxylic acids (). A specific example o ...

s: : ''meta''-Chloroperoxybenzoic acid (''m''CPBA) is prepared in this way: Chlorperoxybenzoic acid synthesis

A related method starts with the peroxyanhydride. Aromatic

aldehydes In organic chemistry, an aldehyde () (lat. ''al''cohol ''dehyd''rogenatum, dehydrogenated alcohol) is an organic compound containing a functional group with the structure . The functional group itself (without the "R" side chain) can be referred ...

can be autoxidized to give peroxycarboxylic acids: : (Ar =

aryl In organic chemistry, an aryl is any functional group or substituent derived from an aromatic ring, usually an aromatic hydrocarbon, such as phenyl and naphthyl. "Aryl" is used for the sake of abbreviation or generalization, and "Ar" is used ...

group) The products, however, react with the initial aldehyde forming the carboxylic acid: :

Properties and uses

In terms of acidity, peroxycarboxylic acids are about 1000 times weaker than the parent carboxylic acid, due to the absence of

resonance Resonance is a phenomenon that occurs when an object or system is subjected to an external force or vibration whose frequency matches a resonant frequency (or resonance frequency) of the system, defined as a frequency that generates a maximu ...

stabilization of the anion. For similar reasons, their p''K''_a values tend also to be relatively insensitive to substituents. The most common use of organic peroxy acids is for the conversion of alkenes to epoxides, the

Prilezhaev reaction The Prilezhaev reaction, also known as the Prileschajew reaction or Prilezhaev epoxidation, is the chemical reaction of an alkene with a peroxy acid to form epoxides. It is named after Nikolai Prilezhaev, who first reported this reaction in 1909 ...

Another common reaction is conversion of cyclic ketones to the ring-expanded esters using peracids in a Baeyer-Villiger oxidation. They are also used for the oxidation of

amine In chemistry, amines (, ) are organic compounds that contain carbon-nitrogen bonds. Amines are formed when one or more hydrogen atoms in ammonia are replaced by alkyl or aryl groups. The nitrogen atom in an amine possesses a lone pair of elec ...

s and

thioether In organic chemistry, a 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 organic compound, volatile sulfides have ...

s to

amine oxide In chemistry, an amine oxide, also known as an amine ''N''-oxide or simply ''N''-oxide, is a chemical compound that has the chemical formula . It contains a nitrogen-oxygen coordinate covalent bond with three additional hydrogen and/or substitue ...

s and

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. The laboratory applications of the valued reagent ''m''CPBA illustrate these reactions. Reaction of peroxycarboxylic acids with acid chlorides affords diacyl peroxides: : The oxidizing tendency of peroxides is related to the

electronegativity Electronegativity, symbolized as , is the tendency for an atom of a given chemical element to attract shared electrons (or electron density) when forming a chemical bond. An atom's electronegativity is affected by both its atomic number and the ...

of the substituents.

Electrophilic In chemistry, an electrophile is a chemical species that forms bonds with nucleophiles by accepting an electron pair. Because electrophiles accept electrons, they are Lewis acids. Most electrophiles are positively charged, have an atom that carr ...

peroxides are stronger oxygen-atom transfer agents. The oxygen-atom donor tendency correlates with the

acidity An acid is a molecule or ion capable of either donating a proton (i.e. hydrogen cation, H+), known as a Brønsted–Lowry acid, or forming a covalent bond with an electron pair, known as a Lewis acid. The first category of acids are the ...

of the bond. Thus, the order of oxidizing power is .

Usage

Peroxycarboxylic acids are available in both solid and liquid forms. Due to their oxidizing and disinfecting properties, they can be used in both professional and domestic settings.

Bleaching Agents

Peroxycarboxylic acids are bleaching agents and are used globally, particularly for tooth whitening. They are employed in various concentrations in dentistry to effectively bleach teeth. Lower concentrations are common for home use. Compared to hydrogen peroxide, peroxycarboxylic acids are approved as cosmetics in Europe under Regulation (EC) No. 1223/2009 of the European Parliament.

Desinfectants

In healthcare, peroxycarboxylic acids are primarily used for wound disinfection and cleaning contact lenses. Peroxycarboxylic acids are also found in cleaning agents, disinfectants, and detergents, as they reliably kill germs and bacteria.

References

{{DEFAULTSORT:Peroxy Acid Organic peroxy acids