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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 · 2022 · Mains Paper III

Q7(c). Lactic acid from ethanal through the cyanohydrin

Question

How can the following compound be prepared from a carbonyl compound that has one less carbon than the designed product? [structure of lactic acid given in the paper]

Answer in brief

From ethanal (CH₃CHO): HCN adds to give the cyanohydrin CH₃CH(OH)CN; acid hydrolysis of –CN gives 2-hydroxypropanoic acid (lactic acid).

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

Coverscyanohydrinlactic acidHCN additionnitrile hydrolysisacetaldehyde

All parts of Question 7