Q7 · CSIR-NET Chemistry, June 2017
Paper: CSIR-NET June 2017 · Subject: Organic Chemistry · Chapter: Organic Spectroscopy · Topic: Combined Structure Elucidation · Marks: 2 · Difficulty: Hard
The correct structure of the compound based on the following characteristic spectral data is IR: $1736\,\mathrm{cm}^{-1}$ $^{1}\mathrm{H}$ NMR: $\delta$ 3.59 (s, 3H), 3.32 (t, 2H), 2.25 (t, 2H), 1.85-1.75 (m, 2H), 1.73-1.62 (m, 2H) $^{13}\mathrm{C}$ NMR: $\delta$ 174.0, 51.0, 32.9, 32.9, 32.8, 31.0, 23.0
(a)
(b)
(c)
(d)
Answer
Answer: B ✓ checked by 4AB · confidence high
Explanation
IR 1736 cm⁻¹ = ester; δ 3.59 (s, 3H) and 51.0 = OCH₃ (an OEt would give a quartet); 3.32 (t, 2H) = CH₂Br; 2.25 (t, 2H) = CH₂CO; two more CH₂ multiplets. That is methyl 5-bromopentanoate, structure (b). A CHBr (d) would be a multiplet, an acetate (c) would show a CH₃CO singlet at ~2.0.
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