UPSC Combined Geo-Scientist
Chemist
- 3 descriptive papers
- 200 marks each
- 3 h per paper
Mains Paper III covers analytical and organic chemistry.
All years
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Mains Paper III, analytical and organic chemistry
Question paper, 2024
UPSC Combined Geo-Scientist, Stage II (Mains). 8 pages, as issued by UPSC.
Every question of 2024, one page each54 parts in 10 questions, with the question as text and the key points of its answer
Question 1 40 marks
- 1(a)Percentage relative error of a balance reading5 marks
- 1(b)Partition ratio k′ and relative retention α5 marks
- 1(c)Transmittance from Beer’s law5 marks
- 1(d)Identifying a magnesium compound from its thermogram5 marks
- 1(e)Properties needed in a detector for X-ray fluorescence5 marks
- 1(f)Generation of the plasma in the ICP torch5 marks
- 1(g)Calorific value of a fuel5 marks
- 1(h)AAS and ICP compared: accuracy, interferences, detection limit5 marks
Question 2 30 marks
Question 3 30 marks
Question 4 30 marks
Question 5 30 marks
Question 6 40 marks
- 6(a)Curtius rearrangement; the isocyanate closes to a cyclic urea4 marks
- 6(b)HBr and a conjugated diene: 1,2- and 1,4-addition4 marks
- 6(c)Phenylglycine and mandelic acid from benzaldehyde4 marks
- 6(d)Coumarin and 3-acetylcoumarin from salicylaldehyde4 marks
- 6(e)Intramolecular oxymercuration–demercuration: a cyclic ether4 marks
- 6(f)trans- and cis-Cyclohexane-1,2-diol from cyclohexanone4 marks
- 6(g)[1,5]-Carbon shift and Cope rearrangement4 marks
- 6(h)Four C₁₀H₁₄ isomers: the one marked by a McLafferty peak4 marks
- 6(i)C₃H₇NO with two N–methyl singlets: N,N-dimethylformamide4 marks
- 6(j)ν(C=C) of methylidenecycloalkanes and ring size4 marks
Question 7 30 marks
- 7(a)(i)Schmidt reaction of a cyclohexanone with an alkyl azide5 marks
- 7(a)(ii)Robinson annulation of 2-methylcyclohexane-1,3-dione5 marks
- 7(b)Oxepin: 6π electrocyclic ring closure, then Diels–Alder addition5 marks
- 7(c)Chloromethylation, then Sommelet–Hauser rearrangement5 marks
- 7(d)(i)Iodolactonisation of a cyclopentenylacetic acid5 marks
- 7(d)(ii)Epoxidation, then acid-catalysed ring expansion to a ketone5 marks
Question 8 30 marks
- 8(a)(i)2-Acetylbenzaldehyde with KCN: internal hydride shift to a lactone5 marks
- 8(a)(ii)Hydroboration–oxidation of norbornene: exo-norborneol5 marks
- 8(b)Photolysis of two ketones: Norrish Type II and Type I5 marks
- 8(c)Hexane-2,5-dione with acid: Paal–Knorr furan synthesis5 marks
- 8(d)Ozonolysis, then intramolecular aldol condensation10 marks
Question 9 30 marks
- 9(a)Structure from UV, IR, NMR and mass data: C₇H₈BrN10 marks
- 9(b)Dieckmann condensation, then hydrolysis and decarboxylation5 marks
- 9(c)Beer’s law for camphor; λmax of the methyl halides5 marks
- 9(d)(i)Birch reduction with ring closure: a spiro acid5 marks
- 9(d)(ii)Robinson annulation to a spiro enone5 marks
Question 10 30 marks
- 10(a)(i)Anisole with dibromocarbene: ring expansion to a tropone5 marks
- 10(a)(ii)Benzophenone with aluminium isopropoxide at 250 °C5 marks
- 10(b)Structure from ¹H and ¹³C NMR: C₁₅H₁₄O5 marks
- 10(c)Band width and colour; ν(C=O) of acids and ketones5 marks
- 10(d)(i)Mass spectral fragmentation of an ester and a cyclohexene5 marks
- 10(d)(ii)Structure from IR, ¹H and ¹³C NMR: C₁₀H₉NO₂5 marks