Q89 · CSIR-NET Chemistry, June 2011

Paper: CSIR-NET June 2011 · Subject: Organic Chemistry · Chapter: Organic Spectroscopy · Topic: Organic Spectroscopy – General · Marks: 2 · Difficulty: Easy

The absorption at $\lambda_{\text {max }}=279 \mathrm{nm}(\varepsilon=15)$ in the UV spectrum of acetone is due to
(a)$\pi \rightarrow \pi^{*}$ transition
(b)$n \rightarrow \pi^{*}$ transition
(c)$\sigma \rightarrow \sigma^{*}$ transition
(d)$\pi \rightarrow \sigma^{*}$ transition
Answer
Answer: B ✓ checked by 4AB · confidence high
Explanation
The weak (ε ≈ 15) band of acetone at 279 nm is the symmetry-forbidden n → π* transition of the carbonyl.

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