Annulenes are completely
conjugated monocyclic hydrocarbons. They have the general formula C
nH
n (when
n is an even number) or C
nH
n+1 (when
n is an odd number). The
IUPAC naming conventions are that annulenes with 7 or more carbon atoms are named as [
n]annulene, where
n is the number of
carbon atoms in their ring, though sometimes the smaller annulenes are referred to using the same notation, and benzene is sometimes referred to simply as annulene.