Q7(c)(ii). Mode of ring closure in two electrocyclic reactions
1. Identify the mode of ring closure for each of the following electrocyclic reactions (A) and (B) under heat (Δ). 2. Are the indicated hydrogens cis or trans? [structures of reactions A and B given in the paper]
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
Topic notes: pericyclic reactions, with every Civil Services, IFoS and Geo-Scientist PYQ →
Coverselectrocyclic reactionconrotatorydisrotatoryWoodward–Hoffmann rules4π and 6π
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