Q11 · CSIR-NET Chemistry, June 2013
Paper: CSIR-NET June 2013 · Subject: Organic Chemistry · Chapter: Natural Products · Topic: Terpenoids · Marks: 2 · Difficulty: Medium
Under review — part of this question (a structure or an option) is not clear in the source scan. 4AB is checking it against the original book; the answer shown may change.
In the UV-visible is spectrum, a diterpenoid exhibited $\lambda_{\max }$ at 275 nm . The compound, among the choices given below is
(a)
(b)
Answer
Under review — not yet confirmed.
Answer: B
The source book printed C; on checking, B is correct — see the explanation.
Explanation
λmax ≈ 275 nm fits a homoannular (both double bonds in one ring) diene (Woodward base 253 nm plus ring residues); the heteroannular s-trans diene of (a) would absorb near 240 nm.
Study loop for Natural Products