Q7(a). C₆H₁₀O from UV, IR and ¹H NMR: mesityl oxide
An organic liquid with molecular formula C₆H₁₀O gave the following spectral data:
UV: νmax 230 nm (ε 12600), 329 nm (ε 41)
IR: νmax 2950–2860 (m), 1695 (s), 1620 (m), 1460 (m) cm⁻¹
NMR: δ 1.9 (s, 3H), 2.1 (s, 6H), 6.15 (s, 1H)
Write the possible structure of compound with suitable justification. Predict its ¹³C-NMR spectrum.
Answer in brief
The compound is mesityl oxide, 4-methylpent-3-en-2-one, (CH₃)₂C=CH-CO-CH₃ : DBE 2, conjugated enone (UV 230/329 nm; calc. 239 nm; IR 1695, 1620 cm⁻¹), three methyl singlets and one vinylic singlet. Predicted ¹³C: δ ≈ 198, 155, 124, 31, 28, 21 (six lines) .
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Coversdegree of unsaturationintense π→π*weak n→π*sp³ C–Hvinylic α-H
All parts of Question 7
- 7(a) C₆H₁₀O from UV, IR and ¹H NMR: mesityl oxide20 marks
- 7(b) ¹H NMR of p-xylene and ethylbenzene10 marks
- 7(c) ESR spectra of three aromatic radicals10 marks