Q140 · CSIR-NET Chemistry, June 2011
Paper: CSIR-NET June 2011 · Subject: Physical Chemistry · Chapter: Quantum Chemistry · Topic: Quantum Chemistry – General · Marks: 2 · Difficulty: Medium
The energy levels for cyclobutadiene are $\alpha+2 \beta, \alpha, \alpha$ and $\alpha-2 \beta$. The delocalization energy in this molecule is:
(a)0
(b)$-4 \beta$
(c)$-8 \beta$
(d)$4 \alpha$
Answer
Answer: A ✓ checked by 4AB · confidence high
The source book printed no answer; this one was worked out and checked — see the explanation.
Explanation
Four π electrons: 2(α + 2β) + 2α = 4α + 4β, equal to two isolated ethylenes 2(2α + 2β): delocalisation energy zero.
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