Q10(c)(i). Structure from IR, ¹H and ¹³C NMR: C₉H₈O₂
An organic compound with molecular formula C₉H₈O₂ gives following spectral data: IR: broad band between 3000 and 2500 cm⁻¹; 1680 cm⁻¹. ¹H NMR: δ 11.0 (s, broad, 1H); 7.8 (d, 1H, J = 16.1 Hz); 7.55–7.40 (m, 5H); 6.5 (d, 1H, J = 16.1 Hz). ¹³C NMR: 173, 147, 134, 133, 131, 129, 128, 127, 117. Deduce the structure and interpret the spectral data.
Model answer
The free solution for 2025 answers questions 1, 2, 4, 6, 7 and 9, the ones picked in its time plan. Question 10 is answered in full in the Geo-Scientist Chemistry Paper III, 2021 to 2025 book, with every part of every paper.
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UPSC Combined Geo-Scientist (Main) Chemistry Paper III: Model Answers 2021 to 2025
- All ten questions of each paper, with the question printed above its answer
- Instruments drawn as labelled diagrams, numericals worked with units
- Topic-wise weightage and a topic-wise index
Coverscinnamic acidtrans coupling constantα,β-unsaturated acid1H NMRIR carboxylic acid
All parts of Question 10
- 10(a)(i) para-Claisen rearrangement of an allyl aryl ether5 marks
- 10(a)(ii) Electrocyclic ring closure and Diels–Alder cycloaddition5 marks
- 10(b)(i) Woodward–Fieser rules: two ketones, 249 nm and 287 nm5 marks
- 10(b)(ii) Structure from IR bands and two chemical tests: M = 1085 marks
- 10(c)(i) Structure from IR, ¹H and ¹³C NMR: C₉H₈O₂5 marks
- 10(c)(ii) Mass spectrum: benzyl acetate or ethyl benzoate5 marks