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JEE Main levelSingle correct optionDifficulty 2 of 3g1068

Which of the following cations is the most stable?

Acyclopropyl cation, $c - C X_{3} H X_{5} X^{+}$
Bcyclopenta-2,4-dien-1-ylium (cyclopentadienyl cation)
Ccyclohexyl cation, $c - C X_{6} H X_{11} X^{+}$
Dcyclohepta-2,4,6-trien-1-ylium (tropylium cation)

Answer: D

The tropylium ion is planar, cyclic and fully conjugated with 6

π

electrons, so it is aromatic and exceptionally stable. The cyclopentadienyl cation has 4

π

electrons (antiaromatic). The cyclopropyl and cyclohexyl cations are non-aromatic and have no resonance delocalisation.

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