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Criegee rearrangement

 
Criegee Rearrangement

 
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Criegee rearrangement
 
 
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The Criegee rearrangement is a rearrangement reaction
Rearrangement reaction

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 ....
 named after Rudolf Criegee
Rudolf Criegee

Rudolf Criegee was a German chemist. He studied in T?bingen, Greifswald, and W?rzburg and received his doctorate at W?rzburg in 1925. He proposed a reaction mechanism for ozonolysis in 1953....
. In this organic reaction
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 and organic redox reaction....
 a tertiary alcohol is cleaved in an organic oxidation by a peroxyacid to a ketone
Ketone

In organic chemistry, a ketone is a type of organic compound which contains a carbonyl group bonded to two other carbon atoms in the form:Neither of the substituents R1 and R2 may be equal to hydrogen ....
. 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
Baeyer-Villiger oxidation

The Baeyer-Villiger oxidation is an organic reaction in which a ketone is redox to an ester by treatment with peroxy acids or hydrogen peroxide....
 where the intermediate hydroxyperacid is called a Criegee intermediate.






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The Criegee rearrangement is a rearrangement reaction
Rearrangement reaction

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 ....
 named after Rudolf Criegee
Rudolf Criegee

Rudolf Criegee was a German chemist. He studied in T?bingen, Greifswald, and W?rzburg and received his doctorate at W?rzburg in 1925. He proposed a reaction mechanism for ozonolysis in 1953....
. In this organic reaction
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 and organic redox reaction....
 a tertiary alcohol is cleaved in an organic oxidation by a peroxyacid to a ketone
Ketone

In organic chemistry, a ketone is a type of organic compound which contains a carbonyl group bonded to two other carbon atoms in the form:Neither of the substituents R1 and R2 may be equal to hydrogen ....
. The acid used is often p-nitroperoxybenzoic acid because the p-nitrobenzoic acid anion is a good leaving group.

Criegee Rearrangement


The reaction mechanism has similarities with the Baeyer-Villiger oxidation
Baeyer-Villiger oxidation

The Baeyer-Villiger oxidation is an organic reaction in which a ketone is redox to an ester by treatment with peroxy acids or hydrogen peroxide....
 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
Carboxylic acid

Carboxylic acids are organic acids characterized by the presence of a carboxyl group, which has the Chemical formula -COH, usually written -COOH or -CO2H....
 leaving behind a carbocation
Carbocation

A carbocation is an ion with a positively-charged carbon atom. The charged carbon atom in a carbocation is a "sextet", i.e. it has only six electrons in its outer Electron shell#Valence shell instead of the eight valence electrons that ensures maximum stability ....
. A hydrolysis
Hydrolysis

Hydrolysis is a chemical reaction during which one or more water are split into hydrogen and hydroxide ions which may go on to participate in further reactions....
 step forms the ketone together with the alcohol. The order of migrationary aptitude is a tert-butyl as the best substituent
Substituent

In organic chemistry, a substituent is an atom or group of atoms substituted in place of a hydrogen atom on the parent chain of a hydrocarbon. The suffix -yl is used when naming organic compounds that contain a substituent....
 followed by isopropyl
Isopropyl

In organic chemistry, isopropyl is a substituent form of propane, the three-carbon alkyl functional group. As an isomer of propyl, bonding to an R group occurs at the secondary carbon....
 then ethyl
Ethyl group

In chemistry, an ethyl group is an alkyl functional group derived from ethane . It has the chemical formula -Carbon2Hydrogen5 and is very often abbreviated -Et....
 and then the methyl group. From this it is inferred that the migrating group carries a partial positive charge in the transition state
Transition state

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 energy along this reaction coordinate....
 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 ortho ester. In the Criegee reaction a vicinal
Vicinal (chemistry)

In chemistry vicinal stands for any two functional groups bonded to two adjacent carbon atoms. For example the molecule 2,3-dibromobutane carries two vicinal bromine atoms and 1,3-dibromobutane does not....
 diol
Diol

A diol or glycol is a chemical compound containing two hydroxyl groups Vicinal diols have hydroxyl groups attached to adjacent atoms. Examples of vicinal diol compounds are ethylene glycol and propylene glycol....
 is cleaved by lead tetraacetate to the corresponding ketones and acetic acid
Acetic acid

Acetic acid, CH3COOH, also known as ethanoic acid, is an organic acid which gives vinegar its sour taste and pungent smell. Pure, water-free acetic acid is a colourless liquid that absorbs water from the environment , and freezes at 16.7 Celsius to a colourless crystalline solid....
.