Epoxides derived from arenes by 1,2-addition of an oxygen atom to a formal double bond, e.g. 5,6-epoxycyclohexa-1,3-diene.
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(Common usage has extended the term to include examples with the epoxy group bridging nonadjacent atoms.)
Source:
PAC, 1995, 67, 1307. 'Glossary of class names of organic compounds and reactivity intermediates based on structure (IUPAC Recommendations 1995)' on page 1318 (https://doi.org/10.1351/pac199567081307)