Question

The cyclic \(π\)-molecular orbital formed by overlap of p-orbitals must contain,

• A. \((4n+2)\) p electrons.
• B. \((2n+2)\) p electrons.
• C. \((4n-2)\) p electrons.
• D. \((2n-2)\) p electrons.

Hint:

Huckel rule for aromatic stability needs 4n+2 pi electrons.

Answer 1

The Correct Option is A

Step 1: Recall the rule.
Erich Huckel showed that planar, cyclic, fully conjugated rings with $(4n+2)$ pi electrons are aromatic.

Step 2: Test with examples.
Benzene has 6 electrons, so $n = 1$. The cyclopentadienyl anion has 6. Naphthalene has 10, so $n = 2$. All fit $4n+2$.

Step 3: Why not the others.
$2n+2$ would allow 4 electrons, which makes cyclobutadiene look aromatic when it is anti-aromatic. The forms $4n-2$ and $2n-2$ have no basis in the rule.

Final Answer:
Option (A) is correct. \[ \boxed{(4n+2)} \]