The three species cyclopentadienyl cation, cyclopentadienyl radical and cyclopentadienyl anion (each planar, $C X_{5} H X_{5}$ with charge +, none, -) are compared. The correct order of stability is:

Aradical > anion > cation
Banion > cation > radical
Canion > radical > cation
Dcation > radical > anion

Answer: C

The anion has 6 pi electrons (4n+2) and is aromatic. The cation has 4 pi electrons (4n) and is antiaromatic and destabilised. The radical has 5 pi electrons, neither aromatic nor antiaromatic, so it lies between them.

Practice General Organic Chemistry I: Electronic Effects More on Applications: stability of carbocations, carbanions, free radicals

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The three species cyclopentadienyl cation, cyclopentadienyl radical and cyclopentadienyl anion (each planar, CX5​HX5​ with charge +, none, -) are compared. The correct order of stability is:

Answer: C

More questions on Applications: stability of carbocations, carbanions, free radicals

The three species cyclopentadienyl cation, cyclopentadienyl radical and cyclopentadienyl anion (each planar, $C X_{5} H X_{5}$ with charge +, none, -) are compared. The correct order of stability is: