UPSC Civil Services (Mains), Chemistry optional · 2024 · Paper II
Q1(d). Name and reagent for five conversions
Question
Write the name of the reaction and reagent required for the following conversions (i) to (v). [five conversion schemes given in the paper; (iv) forms H₂C=CH₂ as a product]
Answer in brief
(i) Baeyer–Villiger oxidation, m-CPBA; (ii) Wolff–Kishner reduction, N₂H₄/KOH; (iii) Dieckmann condensation, NaOMe; (iv) Hofmann elimination, Ag₂O/H₂O, Δ; (v) Cannizzaro reaction, conc. NaOH.
Key points
- (i) Ketone to lactone: peracid inserts O beside C=O through the Criegee intermediate.
- (ii) C=O to CH₂ in base: hydrazone loses N₂; 2° OH survives (not so with Zn–Hg / HCl).
- (iii) Diester to cyclic β-keto ester: intramolecular Claisen; five-membered ring.
- (iv) Quaternary ammonium hydroxide, heat: E2, anti β-H; NMe₃ leaves.
- (v) Aldehyde without α-H: hydride transfer; one molecule oxidised, one reduced.
The full model answer
As written for the answer booklet: the diagram carries the working, the lines stay short. Read here only; it is not offered as a download.
CoversBaeyer–Villiger oxidationWolff–Kishner reductionDieckmann condensationHofmann eliminationCannizzaro reactionnamed reactions
All parts of Question 1
- 1(a)(i) Aromatic, non-aromatic or antiaromatic5 marks
- 1(a)(ii) Diphenylcyclopropenone resists nucleophilic addition5 marks
- 1(b) Intermediate in the amination of bromobenzene10 marks
- 1(c) (S)-2-Butanol to (S)-2-butyl chloride10 marks
- 1(d) Name and reagent for five conversions10 marks
- 1(e) Electrocyclic steps of cyclononatriene10 marks