UPSC Civil Services (Mains)
Chemistry optional
- 2 papers
- 250 marks each
- 3 h per paper
- 5 of 8 questions, Q1 and Q5 compulsory
Paper II covers organic chemistry and spectroscopy.
All years
Pages 1 and 2 of 25 
Pages 3 and 4 of 25 
Pages 5 and 6 of 25
Pages 7 and 8 of 25 Pages 9 and 10 of 25 Pages 11 and 12 of 25 Pages 13 and 14 of 25 Pages 15 and 16 of 25 Pages 17 and 18 of 25 Pages 19 and 20 of 25 Pages 21 and 22 of 25 Pages 23 and 24 of 25 Page 25 of 25 
Paper II, organic chemistry and spectroscopy
Solution, 2021
UPSC Civil Services (Mains), Chemistry optional. 25 pages. Questions 1, 2, 3, 5 and 8 are answered.
Every question of 2021, one page each40 parts in 8 questions, with the question as text and the key points of its answer
Question 1 50 marks
- 1(a)Origin of the CN group in RCOO⁻ + BrCN10 marks
- 1(b)Benzyltrimethylammonium salt with sodium amide at low and at high temperature10 marks
- 1(c)2-Cyclohexylpropan-2-ol with BF₃·OEt₂: products A and B10 marks
- 1(d)Two aldehydes towards a nucleophile in the presence of BF₃·OEt₂10 marks
- 1(e)Two transformations by electrocyclic relays10 marks
Question 2 50 marks
- 2(a)Elimination from trans- and cis-1-chloro-2-methylcyclohexane20 marks
- 2(b)Cyclopropylmethyl cation; acidity of two 1,3-diones; a diazo ester heated in cyclohexane15 marks
- 2(c)(i)1-Phenylethanol with SOCl₂ and pyridine10 marks
- 2(c)(ii)Cyclohexanone enolate with methyl iodide and with trimethylsilyl chloride5 marks
Question 3 50 marks
- 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
Question 4 50 marks
- 4(a)(i)Deuterium scrambling on heating 3-deuteroindene10 marks
- 4(a)(ii)Cyclopentadiene with maleic anhydride10 marks
- 4(b)(i)3,3-Dimethylbut-1-ene with HCl5 marks
- 4(b)(ii)Allyl bromide with HBr, without and with benzoyl peroxide10 marks
- 4(c)(i)A Wittig reaction and a Fischer indole synthesis10 marks
- 4(c)(ii)Pairs that give an α,β-unsaturated carbonyl compound with base5 marks
Question 5 50 marks
- 5(a)Five ¹H NMR signals of pentane-2,4-dione10 marks
- 5(b)(i)Three para-substituted styrenes in anionic polymerisation5 marks
- 5(b)(ii)Structures and configurations of natural and synthetic rubber5 marks
- 5(c)Acetophenone with SeO₂; benzoic acid with Na in liquid NH₃10 marks
- 5(d)Ease of Norrish type II hydrogen abstraction in two groups of ketones10 marks
- 5(e)McLafferty rearrangement in pentan-2-one; base peak of pentan-3-one10 marks
Question 6 50 marks
- 6(a)(i)Product of acetone with dilute sodium hydroxide from its spectra15 marks
- 6(a)(ii)Higher carbonyl stretching frequency in two pairs5 marks
- 6(b)Interactions that stabilise a protein, with the residues involved15 marks
- 6(c) IPhotolysis of 2-cyclopropylcyclohexanone5 marks
- 6(c) IIPhotolysis of 1,1,3-triphenylpropan-2-one10 marks
Question 7 50 marks
Question 8 50 marks
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Model answer pages open with the VKC plan.
Model answer pages open with the VKC plan.
Model answer pages open with the VKC plan.
Model answer pages open with the VKC plan.
Model answer pages open with the VKC plan.
Model answer pages open with the VKC plan.
Model answer pages open with the VKC plan.
Model answer pages open with the VKC plan.
Printed copy and Kindle
UPSC Civil Services (Main) Chemistry Paper II: Model Answers 2021 to 2025
The book has all five years of Paper II in one volume, with every question printed above its answer, mechanisms labelled on the scheme, the topic-wise weightage of marks and a topic-wise index.