Alkenes react with peracids (peroxyacids) to form epoxides. Epoxides are three-membered cycles that contain oxygen.
![epoxidation of alkenes epoxidación de alquenos](/images/stories/organica-i/alquenos-reacciones/epoxidacion/epoxidacion-alquenos01.png)
The most common reagent in this reaction is peroxyacetic acid, although MCPBA can also be used. The most commonly used solvents are dichloromethane and chloroform.
The epoxidation of alkenes is chemoselective, reacting better with more substituted alkenes.
![epoxidation of alkenes epoxidación de alquenos](/images/stories/organica-i/alquenos-reacciones/epoxidacion/epoxidacion-alquenos02.png)
It also presents a high diastereoselectivity, better epoxidizing the less hindered face of the alkene.
![epoxidation alkenes03](/images/stories/organica-i/alquenos-reacciones/epoxidacion/epoxidacion-alquenos03.png)
[1] Majority. Epoxidation on the less impeded side.
[2] Minority.
The mechanism of the epoxidation of alkenes is concerted, taking place in a single stage.
![epoxidation of alkenes epoxidación de alquenos](/images/stories/organica-i/alquenos-reacciones/epoxidacion/epoxidacion-alquenos04.png)