''meta''-Chloroperoxybenzoic acid (mCPBA or ''m''CPBA) is a

peroxycarboxylic acid A peroxy acid (often spelled as one word, peroxyacid, and sometimes called peracid) is an acid which contains an acidic group. The two main classes are those derived from conventional mineral acids, especially sulfuric acid, and the peroxy deri ...

. It is a white solid often used widely as an

oxidant 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 "Electron acceptor, accepts"/"receives" an electron from a (called the , , or ''electr ...

organic synthesis Organic synthesis is a branch of chemical synthesis concerned with the construction of organic compounds. Organic compounds are molecules consisting of combinations of covalently-linked hydrogen, carbon, oxygen, and nitrogen atoms. Within the gen ...

. mCPBA is often preferred to other peroxy acids because of its relative ease of handling. mCPBA is a strong oxidizing agent that may cause fire upon contact with flammable material.

Preparation and purification

mCPBA can be prepared by reacting m-chlorobenzoyl chloride with a basic solution of

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 ...

, followed by acidification. It is sold commercially as a shelf-stable mixture that is less than 72% mCPBA, with the balance made up of ''m''-chlorobenzoic acid (10%) and water. The peroxyacid can be purified by washing the commercial material with a sodium hydroxide and potassium phosphate solution buffered at pH = 7.5. Peroxyacids are generally slightly less acidic than their carboxylic acid counterparts, so the acid impurity can be extracted if the pH is carefully controlled. The purified material is reasonably stable against decomposition if stored at low temperatures in a plastic container. In reactions where the exact amount of mCPBA must be controlled, a sample can be titrated to determine the exact amount of active oxidant.

Reactions

The main areas of use are the conversion of

ketone In organic chemistry, a ketone is an organic compound with the structure , where R and R' can be a variety of carbon-containing substituents. Ketones contain a carbonyl group (a carbon-oxygen double bond C=O). The simplest ketone is acetone ( ...

s to

ester In chemistry, an ester is a compound derived from an acid (either organic or inorganic) in which the hydrogen atom (H) of at least one acidic hydroxyl group () of that acid is replaced by an organyl group (R). These compounds contain a distin ...

s ( Baeyer-Villiger oxidation),

epoxidation In organic chemistry, an epoxide is a cyclic ether, where the ether forms a three-atom ring: two atoms of carbon and one atom of oxygen. This triangular structure has substantial ring strain, making epoxides highly reactive, more so than other ...

alkenes In organic chemistry, an alkene, or olefin, is a hydrocarbon containing a carbon–carbon double bond. The double bond may be internal or at the terminal position. Terminal alkenes are also known as Alpha-olefin, α-olefins. The Internationa ...

(

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 ...

), conversion of silyl enol ethers to silyl α-hydroxy ketones ( Rubottom oxidation), oxidation of

sulfide Sulfide (also sulphide in British English) is an inorganic anion of sulfur with the chemical formula S2− or a compound containing one or more S2− ions. Solutions of sulfide salts are corrosive. ''Sulfide'' also refers to large families o ...

s to sulfoxides and sulfones, and 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 to produce amine oxides. The following scheme shows the epoxidation of

cyclohexene Cyclohexene is a hydrocarbon with the formula . It is a cycloalkene. At room temperature, cyclohexene is a colorless liquid with a sharp odor. Among its uses, it is an chemical intermediate, intermediate in the commercial synthesis of nylon. Prod ...

with mCPBA. : Reaction of cyclohexene with mCPBA

The epoxidation mechanism is concerted: the ''cis'' or ''trans'' geometry of the alkene starting material is retained in the epoxide ring of the product. The transition state of the Prilezhaev reaction is given below: Mcpbaepoxidation-updated

The geometry of the transition state, with the peracid bisecting the C-C double bond, allows the two primary frontier orbital interactions to occur: π_C=C (HOMO) to σ*_O-O (LUMO) and n_O (HOMO, regarded as a filled p orbital on a sp² hybridized oxygen) to π*_C=C (LUMO), corresponding, in arrow-pushing terms, to formation of one C-O bond and cleavage of the O-O bond and formation of the other C-O bond and cleavage of the C=C π bond.

References

{{DEFAULTSORT:Chloroperoxybenzoic acid, meta- 3-Chlorophenyl compounds Organic peroxy acids Reagents for organic chemistry