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| Names | |||
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| Preferred IUPAC name 3-Chlorobenzene-1-carboperoxoic acid | |||
Other names
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| Identifiers | |||
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3D model (JSmol) | |||
| ChemSpider |
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| ECHA InfoCard | 100.012.111 | ||
| EC Number |
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| RTECS number |
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| UNII | |||
| UN number | 3106 | ||
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| Properties | |||
| C7H5ClO3 | |||
| Molar mass | 172.56 g·mol−1 | ||
| Appearance | White powder | ||
| Melting point | 92 to 94 °C (198 to 201 °F; 365 to 367 K) decomposes | ||
| Acidity (pKa) | 7.57 | ||
| Hazards | |||
| Occupational safety and health (OHS/OSH): | |||
Main hazards | Oxidizing, corrosive, explosive | ||
| GHS labelling: | |||
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| Danger | |||
| H226,H314,H335 | |||
| P210,P220,P233,P234,P240,P241,P242,P243,P260,P264,P271,P272,P280,P301+P330+P331,P302+P352,P303+P361+P353,P304+P340,P305+P351+P338,P310,P312,P321,P332+P313,P333+P313,P337+P313,P362,P363,P370+P378,P403+P233,P403+P235,P405,P411,P420,P501 | |||
| Related compounds | |||
Related compounds | peroxyacetic acid;peroxybenzoic acid | ||
Except where otherwise noted, data are given for materials in theirstandard state (at 25 °C [77 °F], 100 kPa). | |||
meta-Chloroperoxybenzoic acid (mCPBA ormCPBA) is aperoxycarboxylic acid. It is a white solid often used widely as anoxidant inorganic synthesis. mCPBA is often preferred to other peroxy acids because of its relative ease of handling.[1] mCPBA is a strong oxidizing agent that may cause fire upon contact with flammable material.[2]
mCPBA can be prepared by reacting m-chlorobenzoyl chloride with a basic solution ofhydrogen peroxide, followed by acidification.[3]
It is sold commercially as a shelf-stable mixture that is less than 72% mCPBA, with the balance made up ofm-chlorobenzoic acid (10%) and water.[1] The peroxyacid can be purified by washing the commercial material with a sodium hydroxide and potassium phosphate solution buffered at pH = 7.5.[2][4] Peroxyacids are generally slightly less acidic than their carboxylic acid counterparts, so the acid impurity can be extracted if thepH 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 betitrated to determine the exact amount of active oxidant.
The main areas of use are the conversion ofketones toesters (Baeyer-Villiger oxidation),epoxidation ofalkenes (Prilezhaev reaction), conversion ofsilyl enol ethers tosilylα-hydroxy ketones (Rubottom oxidation), oxidation ofsulfides tosulfoxides andsulfones, and oxidation ofamines to produceamine oxides. The following scheme shows the epoxidation ofcyclohexene with mCPBA.
Theepoxidation mechanism is concerted: thecis ortrans 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:[5]
The geometry of the transition state, with the peracid bisecting the C-C double bond, allows the two primary frontier orbital interactions to occur: πC=C (HOMO) to σ*O-O (LUMO) and nO (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.
