Chemistry · Aldehyde and Ketones: Nature of carbonyl group, nucleophilic addition to >C=O group, relative reactivities of aldehydes and ketones

Cyanohydrin of which compound on hydrolysis will give lactic acid?

Cyanohydrin of which compound on hydrolysis will give lactic acid?

  • A. \( C_{6} H_{5} C H O \)
  • B. \( H C H O \)
  • C. \( C H_{3} C H O \)
  • D. \( C H_{3} C H_{2} C H O \)

Step-by-step solution

Lactic acid (CH3CHOHCOOH) is an α-hydroxy acid. Cyanohydrin formation from an aldehyde followed by hydrolysis yields an α-hydroxy acid. To obtain lactic acid, the starting aldehyde must be acetaldehyde (CH3CHO), which after cyanohydrin addition gives CH3CHOHCN, and hydrolysis produces lactic acid. Options A, B, and D give different α-hydroxy acids.
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