JEE Advanced levelOne or more correct optionsDifficulty 3 of 3hc165
Treating each species as fully conjugated, cyclic and planar when that is geometrically possible, which of the following are aromatic according to Huckel's rule?
Acyclopentadienyl cation
Bcyclobutadiene
Ccycloheptatrienyl (tropylium) cation
Dcyclopentadienyl anion
Answer: C, D
Aromatic requires (4n+2) pi electrons: the cyclopentadienyl anion has 6 and the tropylium cation has 6. Cyclobutadiene (4 pi) and the cyclopentadienyl cation (4 pi) are antiaromatic.