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JEE Main levelOne or more correct optionsDifficulty 2 of 3g1217

Assuming each species is planar, which of the following are aromatic?

Acyclopentadienyl anion, $C X_{5} H X_{5} X^{-}$
Bcyclopropenyl cation, $C X_{3} H X_{3} X^{+}$
Ccyclopentadienyl cation, $C X_{5} H X_{5} X^{+}$
Dcycloheptatrienyl cation (tropylium), $C X_{7} H X_{7} X^{+}$

Answer: A, B, D

Aromatic species have a cyclic, planar, fully conjugated system with 4n+2 pi electrons.

C X_{3} H X_{3} X^{+}

has 2,

C X_{5} H X_{5} X^{-}

has 6 and

C X_{7} H X_{7} X^{+}

has 6 pi electrons.

C X_{5} H X_{5} X^{+}

has 4 pi electrons and is antiaromatic.

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