UPSC Combined Geo-Scientist, Mains · 2026 · Mains Paper III
Q7(a). Thermal and photochemical electrocyclisations of cyclooctatriene
Question
Predict the major products (A–C) formed (with appropriate stereochemistry, if any) in the following reaction sequence. Describe the mode of cyclization involved under thermal and photochemical conditions: cycloocta-1,3,5-triene heatAhνBheatC.
Model answer
The free solution for 2026 answers the questions picked in its time plan. Question 7 is answered in full in the Book Edition of the 2026 solutions of Geo-Scientist Chemistry Paper III.
Coverselectrocyclic reactions, Woodward–Hoffmann rules
All parts of Question 7
- 7(a) Thermal and photochemical electrocyclisations of cyclooctatriene10 marks
- 7(b) Bullvalene NMR; quasi-Favorskii rearrangement10 marks
- 7(c) Birch reduction; Michael addition and decarboxylation10 marks