Q15 · CSIR-NET Chemistry, June 2013
Paper: CSIR-NET June 2013 · Subject: Organic Chemistry · Chapter: Organic Spectroscopy · Topic: UV Vis · Marks: 2 · Difficulty: Medium
In the UV-visible is spectrum, a diterpenoid exhibited a $\lambda_{\max }=275 \mathrm{nm}$. The compound, among the choices given below is
(a)
(b)
(c)
(d)
Answer
Answer: C ✓ checked by 4AB · confidence medium
Explanation
Woodward–Fieser: the homoannular diene (c) starts at 253 nm and with its four alkyl/ring residues reaches ≈273–278 nm, matching 275 nm; the heteroannular dienes (a, d) fall near 240 nm (abietic acid 241 nm).
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