Illustrated Glossary of Organic Chemistry

Epoxidation: A process or reaction that gives a molecule an epoxide (oxirane) ring. Most commonly encountered in the conversion of an alkene to an epoxide.

An alkene such as cyclohexene can be epoxidized by reaction with a peracid such as peracetic acid (CH₃CO₃H) or mCPBA. Alkene epoxidation by this method is an electrophilic addition reaction.


Benzo[a]pyrene is a human carcinogen. Benzo[a]pyrene is nonpolar so the body oxidizes it to increase its polarity and allow for faster excretion. In the liver benzo[a]pyrene is epoxidized by an enzyme, then hydrolyzed, and again epoxidized as shown above. The epoxide diol product is susceptible to nucleophilic addition by a guanine amino group in DNA, resulting in DNA alkylation, DNA mutation, and other problems.