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Epoxidation of Alkenes with Peracids

Epoxidation of Alkenes with Peracids: Substituent Effects

Relative reaction rates for the epoxidation of alkenes

The outcome of the epoxidation of a double bond is determined by the substituents; the effect of solvent polarity on the reaction rate is negligible. However, protic solvents prevent the formation of the hydrogen bond. Therefore, chlorinated hydrocarbons are mostly used. Electron-donating substituents at the C=C double bond, for example alkyl groups, increase the rate of addition of the electrophilic oxygen atom.

Fig.1
Relative rates of epoxidation

Electron-withdrawing substituens have the opposite effect.

Since the reaction in principle is an electrophilic addition, reaction rates also increase if the peracid contains electron-withdrawing substituents.

Fig.2
Electron-withdrawing substituents
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