Q8(c)(i). [1,5]-Hydrogen shift, then ring opening of a cyclobutene
Complete the following reaction and identify A and B. Give justification. [starting compound given in the paper; 200 °C → A; 260 °C → B]
Model answer
The free solution for 2025 answers questions 1, 2, 4, 6, 7 and 9, the ones picked in its time plan. Question 8 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
Topic notes: pericyclic reactions, with every Civil Services, IFoS and Geo-Scientist PYQ →
Covers[1,5]-hydrogen shiftsigmatropic rearrangementcyclobutene ring openingconrotatoryelectrocyclic reaction
All parts of Question 8
- 8(a)(i) 6,6-Dimethylfulvene takes up hydride; a simple alkene does not5 marks
- 8(a)(ii) Doped and non-doped conducting polymers; polyacetylene5 marks
- 8(b)(i) Wittig alkene, then epoxide and diol5 marks
- 8(b)(ii) Ozonolysis, then intramolecular aldol condensation5 marks
- 8(c)(i) [1,5]-Hydrogen shift, then ring opening of a cyclobutene5 marks
- 8(c)(ii) Oxy-Cope rearrangement of a bicyclic vinyl carbinol5 marks