UPSC Combined Geo-Scientist, Mains · 2024 · Mains Paper III

Q9(d)(ii). Robinson annulation to a spiro enone

5 marks
Topic: Reactions at the carbonyl group
Answered

Question

Formulate the products and mechanisms of the following reactions: (ii) [structure of the aldehyde given in the paper] + CH₂=CH–CO–CH₃, CH₃ONa/CH₃OH → ?

Answer in brief

Spiro[5.5]undec-1-en-3-one (+ H₂O): Michael addition, then intramolecular aldol condensation.

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Topic notes: carbonyl additions and condensations, with every Civil Services, IFoS and Geo-Scientist PYQ →

CoversRobinson annulationMichael additionaldol condensationmethyl vinyl ketonespiro enone

All parts of Question 9

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