Q3(a)(i). 1-(Hydroxydiphenylmethyl)cyclopentanol with conc. H₂SO₄
Complete the reaction of 1-(hydroxydiphenylmethyl)cyclopentanol with conc. H₂SO₄, with mechanism. [structure given in the paper]
Answer in brief
Product: 2,2-diphenylcyclohexanone, by a pinacol–pinacolone rearrangement with ring expansion (five- to six-membered ring).
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Topic notes: molecular rearrangements, with every Civil Services, IFoS and Geo-Scientist PYQ →
Coverspinacol–pinacolone rearrangementring expansion1,2-alkyl shiftcarbocation stability2,2-diphenylcyclohexanone
All parts of Question 3
- 3(a)(i) 1-(Hydroxydiphenylmethyl)cyclopentanol with conc. H₂SO₄10 marks
- 3(a)(ii) 1-Acetyl-1-chloro-4-methylcyclohexane with ethoxide10 marks
- 3(b) Cyclopropenyl cation; acidity of indene and cyclopentadiene; tropolones and sydnones15 marks
- 3(c)(i) meso-2,3-Dibromobutane with iodide and with ethoxide5 marks
- 3(c)(ii) 3-Iodo-2,2-dimethylbutane with silver nitrate in hot ethanol10 marks