Alkenes as substituents

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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:

Alkenyl group	Common name	Systematic name
CH₂=CH-	vinyl-	ethenyl
CH₂=CHCH₂-	allyl-	2-propenyl
CH₃CH=CH-		1-propenyl

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 substituent is a C2 alkenyl group i.e. an ethenyl group
The substituent is on C3

3-ethenylhexa-1,4-diene

CH₃CH=CHCH(CH=CH₂)₂

©Dr. Ian Hunt, Department of Chemistry