The Criegee rearrangement is a

rearrangement reaction In organic chemistry, a rearrangement reaction is a broad class of organic reactions where the carbon skeleton of a molecule is rearranged to give a structural isomer of the original molecule. Often a substituent moves from one atom to another ...

named after

Rudolf Criegee Rudolf Criegee (* May 23, 1902 in Düsseldorf; † November 7, 1975 in Karlsruhe) was a German organic chemist. Early life Criegee's family was wealthy. His father worked as a court director. The family was national liberal, Prussian and Prot ...

Description

In this

organic reaction Organic reactions are chemical reactions involving organic compounds. The basic organic chemistry reaction types are addition reactions, elimination reactions, substitution reactions, pericyclic reactions, rearrangement reactions, Mechanistic Organ ...

, a

tertiary alcohol In chemistry, an alcohol is a type of organic compound that carries at least one hydroxyl () functional group bound to a saturated carbon atom. The term ''alcohol'' originally referred to the primary alcohol ethanol (ethyl alcohol), which i ...

is cleaved in an organic oxidation by a

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

to a

ketone In organic chemistry, a ketone is a functional group with the structure R–C(=O)–R', where R and R' can be a variety of carbon-containing substituents. Ketones contain a carbonyl group –C(=O)– (which contains a carbon-oxygen double bo ...

. The acid used is often p-nitroperoxybenzoic acid because the p-nitrobenzoic acid anion is a good leaving group. The reaction mechanism has similarities with the Baeyer-Villiger oxidation where the intermediate hydroxyperacid is called a Criegee intermediate. The per-acid forms a per-ester with the alcohol group. One alkyl substituent migrates from carbon to the adjacent oxygen atom, replacing the

carboxylic acid In organic chemistry, a carboxylic acid is an organic acid that contains a carboxyl group () attached to an R-group. The general formula of a carboxylic acid is or , with R referring to the alkyl, alkenyl, aryl, or other group. Carboxylic ...

leaving behind a

carbocation A carbocation is an ion with a positively charged carbon atom. Among the simplest examples are the methenium , methanium and vinyl cations. Occasionally, carbocations that bear more than one positively charged carbon atom are also encountere ...

. A

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 reaction, substitution, elimination reaction, elimination, and solvation reactions in which water ...

step forms the ketone together with the alcohol. The order of migrationary aptitude is a tert-butyl as the best

substituent A substituent is one or a group of atoms that replaces (one or more) atoms, thereby becoming a moiety in the resultant (new) molecule. (In organic chemistry and biochemistry, the terms ''substituent'' and ''functional group'', as well as ''side ...

followed by

isopropyl In organic chemistry, propyl is a three-carbon alkyl substituent with chemical formula for the linear form. This substituent form is obtained by removing one hydrogen atom attached to the terminal carbon of propane. A propyl substituent is ofte ...

then

ethyl Ethyl may refer to: Arts and entertainment * Cold Ethyl, a Swedish rock band *Ethyl Sinclair, a character in the ''Dinosaurs'' television show Science and technology * Ethyl group, an organic chemistry moiety * Ethyl alcohol (or ethanol) * E ...

and then the

methyl In organic chemistry, a methyl group is an alkyl derived from methane, containing one carbon atom bonded to three hydrogen atoms, having chemical formula . In formulas, the group is often abbreviated as Me. This hydrocarbon group occurs in many ...

group. From this it is inferred that the migrating group carries a partial positive charge in the

transition state In chemistry, the transition state of a chemical reaction is a particular configuration along the reaction coordinate. It is defined as the state corresponding to the highest potential energy along this reaction coordinate. It is often marked wi ...

leading to the carbocation. The consecutive Criegee Rearrangement is carried out in an acidic environment and an ester forms from the carbocation. This opens the way to multiple O-insertion reactions, eventually leading to the orthoester.

References

* Criegee, R., Chem. Ber. 1944, 77, 722. DOI: 10.1002/cber.19450770912 * Criegee, R.; Kaspar, R., Ann. Chem. 1948, 560, 127 * Trifuoroperacetic acid in consecutive Criegee rearrangement and carboxonium ions generation Pavel A. Krasutsky and Igor V. Kolomitsyn Arkivoc 2005 (NZ-1517J) pp 151-17
Article

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publication {{Organic reactions Rearrangement reactions Name reactions