UPSC Civil Services (Mains), Chemistry optional · 2025 · Paper II
Q6(c)(iii). Photolysis of 4,5-dimethylhexan-2-one
Question
Predict the major and minor products for the following photoreaction (hν) of 4,5-dimethylhexan-2-one. Give the logic. [structure given in the paper]
Answer in brief
Major: acetone + 2-methylbut-2-ene; minor: acetone + 3-methylbut-1-ene (and some cyclobutanol), by Norrish type II.
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CoversNorrish type IIγ-hydrogen abstraction1,4-biradicalNorrish–Yangcyclobutanol
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