Question
Write a short note on annulenes.
Solution
Annulenes are monocyclic conjugated polyenes which contain an even number of carbon atoms in their molecules. These are represented by the general formula (-CH = CH-)n where n = 2, 3, 4.....
Aromatic nature in annulenes: According to Huckel’s rule, annulenes containing (4n + 2) electrons and having a coplanar cyclic carbon skeleton should be aromatic in nature. For example,
(i) [4] Annulene. It is non-aromatic because it does not contain 
electrons.
(ii) [6] Annulene. It is aromatic because it contains 
electrons.
(iii) [8] Annulene. It is non-aromatic because it does not contain 
electrons.
