UPSC Civil Services (Mains), Chemistry optional · 2025 · Paper II
Q6(c)(i). Benzene to fulvene by light
Question
Write the mechanism for the following photochemical transformation: benzene → fulvene (hν).
Answer in brief
Benzene (S₁) → prefulvene biradical → fulvene; benzvalene is the co-product.
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Coversbenzene photochemistryfulveneprefulvene biradicalbenzvalenevalence isomerisation
All parts of Question 6
- 6(a)(i) Products and intermediates of two reductions10 marks
- 6(a)(ii) Role of NMO in catalytic dihydroxylation5 marks
- 6(b) Three numericals15 marks
- 6(c)(i) Benzene to fulvene by light5 marks
- 6(c)(ii) Quantum yield of photobromination5 marks
- 6(c)(iii) Photolysis of 4,5-dimethylhexan-2-one5 marks
- 6(c)(iv) A, B and C from the mixed ketones5 marks