Basic IUPAC Organic Nomenclature

Alkenes as substituents

• In some cases, a group containing an alkene may need to be treated as a substituent. 
  
• In these cases the substituent is named in a similar fashion to simple alkyl substituents.
• The method is required when the alkene is not the priority group.
• The substituent is named in a similar way to the parent alkene.
  
• It is named based on the number of carbon atoms in the branch plus the suffix -yl. i.e. alkenyl
• There are two common names that are widely used:
  

Functional group is a (tri) alkene, therefore suffix = -ene The longest continuous chain with 2 C=C is C6 therefore root plus "a" = hexa There are two alkenes in the parent chain, so insert the multiplier di Number from the right as drawn to give the C=C the lowest locants : therefore 1- and 4- The line drawing shows a trans- or E-alkene at C4. The substituent is a C2 alkenyl group i.e. an ethenyl group The substituent is on C3 trans-3-ethenylhexa-1,4-diene or (E)- 3-ethenylhexa-1,4-diene

CH3CH=CHCH(CH=CH2)2

©Dr. Ian Hunt, Department of Chemistry