UPSC Civil Services (Mains), Chemistry optional · 2025 · Paper II
Q7(a)(i). Two UV bands of acetone
Question
Acetone shows a weak absorption at 280 nm and a strong absorption at 190 nm in the UV spectrum. Account for the observation.
Model answer
The free solution for 2025 answers questions 1, 3, 5, 6 and 8, the ones picked in its time plan. Question 7 is answered in full in the Chemistry Paper II, 2021 to 2025 book, with every part of every paper.
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UPSC Civil Services (Main) Chemistry Paper II: Model Answers 2021 to 2025
- All eight questions of each paper, with the question printed above its answer
- Mechanisms drawn out and labelled on the scheme
- Topic-wise weightage and a topic-wise index
Coversn→π* transitionπ→π* transitionUV spectroscopyacetonecarbonyl chromophore
All parts of Question 7
- 7(a)(i) Two UV bands of acetone5 marks
- 7(a)(ii) λmax by the Woodward–Fieser rules10 marks
- 7(b)(i) Diels–Alder reactivity of four dienes10 marks
- 7(b)(ii) 2-Methoxybutadiene with acrylonitrile5 marks
- 7(c)(i) Rearrangement of a cis-divinylcyclopropane10 marks
- 7(c)(ii) Mode of ring closure in two electrocyclic reactions10 marks