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JEE Advanced levelOne or more correct optionsDifficulty 3 of 3o1153

Which of the following statements about cyanohydrin formation from carbonyl compounds are correct?

  1. AAcid hydrolysis of the cyanohydrin gives an alpha-hydroxy carboxylic acid.
  2. BAcetophenone forms its cyanohydrin more favourably than acetaldehyde.
  3. CRate is low in strongly acidic solution because little free is present.
  4. DThe addition is reversible and the cyanohydrin can dissociate again in basic solution.

Answer: A, C, D

Cyanohydrin formation is an equilibrium; base allows loss of from the alkoxide. Hydrolysis of gives next to the OH. In strong acid (pKa 9.2) is not ionised, so the nucleophile is scarce. Aromatic ketones have a less favourable equilibrium than aldehydes, so the last statement is false.
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