Q6(b). Photochemistry of a β-hydroxy bicyclic ketone
Write down the mechanism for the formation of compounds B and C from compound A on photoirradiation. [structures of A, B and C given in the paper]
Answer in brief
Norrish type I α-cleavage gives an acyl–alkyl biradical. Hydrogen transfer one way gives a ketene (then lactone B); the other way gives an unsaturated aldehyde (then lactol C).
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CoversNorrish type Iα-cleavageacyl–alkyl biradicalketenelactonephotochemistry of ketones
All parts of Question 6
- 6(a)(i) Benzoyl peroxide-initiated polymerisation of ethylene10 marks
- 6(a)(ii) Atactic, syndiotactic and isotactic polystyrene5 marks
- 6(b) Photochemistry of a β-hydroxy bicyclic ketone15 marks
- 6(c) A, B, C and D; mechanism of the NaBH₄ step20 marks