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Basic IUPAC Organic Nomenclature

Epoxides

Nomenclature
Formula
3D structure
Functional class name = alkene oxides   e.g. ethylene oxide

Substituent suffix = -ene oxide

Substituent prefix = epoxy-   e.g. epoxyethane

Note: The term oxirane is also used to describe epoxides.


Alkene oxide

Epoxy-

Alkene oxide style:
  • Functional group is an epoxide, therefore suffix = -ene oxide
  • The longest continuous chain is C3 therefore root = prop
  • Location of "alkene" is unambiguous, so no locant needed.
propene oxide

Epoxy style:
  • The longest continuous chain is C3 therefore root = prop
  • The epoxide is a substituent therefore prefix = epoxy
  • Number to give epoxide (only group present) the lowest locants = 1,2-
1,2-epoxypropane
epoxide
Alkene oxide style:
  • Functional group is an epoxide, therefore suffix = -ene oxide
  • The longest continuous chain is C6 therefore root = hex
  • The system is cyclic therefore prefix = cyclo
  • Location of "alkene" is unambiguous, so no locant needed.
cyclohexene oxide

Epoxy style:
  • The longest continuous chain is C6 therefore root = hex
  • The root system is cyclic therefore prefix = cyclo
  • The epoxide is a substituent therefore prefix = epoxy
  • Number to give epoxide (only group present) the lowest locants = 1,2-
1,2-epoxycyclohexane
epoxide

Alkene oxide style:
  • Functional group is an epoxide, therefore suffix = -ene oxide
  • The longest continuous chain is C6 therefore root = hex
  • There is a C1 alkyl substituent = methyl
  • The first point of difference rule requires numbering from the right as drawn to make the "alkene" locant = 2-
  • Hence the methyl group locant = 5-
5-methyl-2-hexene oxide

Epoxy style:
  • The longest continuous chain is C6 therefore root = hex
  • There is a C1 alkyl substituent = methyl
  • The first point of difference rule requires numbering from the right as drawn
  • The epoxide is a substituent therefore prefix = epoxy
  • Number to give epoxide (only group present) the lowest locants = 2,3-
2,3-epoxy-5-methylhexane
epoxide


 © Dr. Ian Hunt, 2005, Department of Chemistry, University of Calgary