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UPSC Combined Geo-Scientist

Chemist

  • 3 descriptive papers
  • 200 marks each
  • 3 h per paper

Mains Paper III covers analytical and organic chemistry.

UPSC Combined Geo-Scientist, Mains · 2025 · Mains Paper III

Q7(a)(i). p-Cresol: Reimer–Tiemann reaction, then a cyanohydrin

Question

p-Cresol (A) reacts with chloroform in alkaline medium to give B which on addition with HCN gives C. The latter on acidic hydrolysis gives chiral carboxylic acid D. Identify A, B, C and D. Name the reaction and give plausible mechanism for conversion of A → B.

Answer in brief

A → B is the Reimer–Tiemann reaction. B = 2-hydroxy-5-methylbenzaldehyde, C = its cyanohydrin, D = 2-hydroxy-2-(2-hydroxy-5-methylphenyl)acetic acid, formed as the racemate.

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Topic notes: reactive intermediates (carbocations, carbanions, radicals, carbenes, nitrenes, benzyne), with every Civil Services, IFoS and Geo-Scientist PYQ →

CoversReimer-Tiemann reactiondichlorocarbenep-cresolcyanohydrinortho-formylation

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