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JEE Main 2025 Jan 23 Shift 1, Chemistry Q13: Molecular Orbital Theory

JEE Main2025Jan 23, Shift 1Chemistry
Q.

The correct stability order of the following species/molecules is :

  1. A

    q r p

  2. B

    r q p

  3. C

    q p r

  4. D

    p q r

Solution

Apply Hückel's rule (planar, cyclic, fully conjugated, -electrons aromatic; -electrons antiaromatic; otherwise non-aromatic).

q (cyclopentadienyl anion): 6 -electrons, planar, fully conjugated. Aromatic - most stable.

r (cyclooctatetraene): 8 -electrons but adopts a tub shape, so it is non-planar and non-aromatic - moderately stable.

p (cyclopropenyl anion): 4 -electrons in a planar conjugated 3-membered ring. Antiaromatic - least stable.

Stability order: q r p.

Concept behind this question

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