The oxirane functional group is a subset of organic cyclic ether compounds. "Cyclic" refers to the fact that the oxirane atoms--two carbons and an oxygen in a three-membered ring--and "ether" that indicates that there is a carbon-oxygen-carbon bonding arrangement. More commonly known as epoxides, the oxirane group is an essential component of many industrial products and processes and is a common functional group introduced during the metabolism of many compounds.

What makes epoxides so useful in synthetic chemistry is the high strain of the ring structure. In this functional group, there is an oxygen atom tenuously connected to two neighboring carbon atoms by single bonds, making a saturated, three-sided ring. The resulting strain on the bonds weakens the carbon-oxygen bond, allowing the epoxide to readily break open the three-membered ring.

Epoxidation, the conversion of an olefin (an unsaturated alkene hydrocarbon) to a cyclic ether...