https://doi.org/10.1351/goldbook.A00433
@[email protected] derived from @[email protected] by 1,2-addition of an oxygen atom to a formal double bond, e.g. 5,6-epoxycyclohexa-1,3-diene.
A00433.png
(Common usage has extended the term to include examples with the epoxy group bridging nonadjacent atoms.)