Criegee rearrangement

Overview

The Criegee rearrangement is a chemical reaction that involves the rearrangement of an ozonide to form a carbonyl compound and a carbonyl oxide. This reaction is named after the German chemist Rudolf Criegee, who first described the mechanism in the mid-20th century. The Criegee rearrangement is a key step in the ozonolysis of alkenes, a process widely used in organic synthesis to cleave carbon-carbon double bonds.

Mechanism

The Criegee rearrangement occurs during the decomposition of the primary ozonide, also known as the molozonide, which is formed when an alkene reacts with ozone. The molozonide is unstable and undergoes a rearrangement to form a more stable ozonide. This ozonide can then decompose to yield a carbonyl compound and a carbonyl oxide, the latter of which is often referred to as a Criegee intermediate.

Diagram of the Criegee rearrangement mechanism.

The mechanism involves a 1,3-dipolar cycloaddition of ozone to the alkene, forming the molozonide. The molozonide then undergoes a concerted rearrangement, breaking the weak O-O bond and forming the ozonide. The ozonide can further decompose, often in the presence of a reducing agent, to yield the final products.

Applications

The Criegee rearrangement is an important reaction in synthetic organic chemistry. It is used to cleave alkenes into smaller carbonyl-containing fragments, which can be further manipulated in various synthetic pathways. This reaction is particularly useful in the synthesis of aldehydes and ketones from alkenes.

In addition to its applications in synthesis, the Criegee rearrangement is also of interest in atmospheric chemistry. Criegee intermediates are believed to play a role in the formation of secondary organic aerosols and in the oxidation of atmospheric pollutants.

Related pages

• Ozonolysis
• Rudolf Criegee
• Carbonyl compound
• Alkene
• Ozone