Criegee rearrangement

Criegee Rearrangement is a significant organic chemistry reaction that involves the ozonolysis of alkenes to form carbonyl compounds. This reaction is named after the German chemist Rudolf Criegee, who first proposed the mechanism in the 20th century. The Criegee rearrangement plays a crucial role in the understanding of ozonolysis and has applications in the synthesis of various organic compounds, including ketones, aldehydes, and carboxylic acids.

Mechanism

The Criegee rearrangement involves several key steps. Initially, the reaction of ozone with an alkene forms a molozonide, which is an unstable intermediate. This molozonide then undergoes a rearrangement to form a more stable ozonide. The critical step in the Criegee mechanism is the cleavage of the ozonide by a reductive or oxidative workup, leading to the formation of carbonyl compounds. Depending on the conditions and the workup procedure, different products can be obtained from the same ozonide intermediate.

Applications

The Criegee rearrangement has found applications in various fields of organic synthesis. It is particularly useful in the synthesis of complex molecules from simpler alkenes, making it a valuable tool in pharmaceutical research and the production of fine chemicals. Additionally, the reaction's ability to cleave double bonds selectively makes it an essential technique for the structural elucidation of natural products.

Environmental Significance

Beyond its applications in organic synthesis, the Criegee rearrangement also has environmental implications. Criegee intermediates are involved in the atmospheric reactions of ozone with alkenes, leading to the formation of secondary organic aerosols. These aerosols play a significant role in atmospheric chemistry and climate, affecting air quality and health.

See Also

• Ozonolysis
• Organic synthesis
• Carbonyl compounds
• Atmospheric chemistry