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JEE MainChemistryAldehydes and Ketones

Benzaldehyde is treated with NaCN followed by heating with ethanol and acid ( H ₃ O ^ ) to yield an intermediate A. Compound A is then reacted with excess phenylmagnesium bromide ( PhMgBr ) followed by acidic workup to give major product B. Identify the IUPAC names of A and B.

Options

  1. AA = 2-Hydroxy-2-phenylethanoic acid ; B = 2-Hydroxy-1,2-diphenylethan-1-one
  2. BA = Ethyl 2-hydroxy-2-phenylethanoate ; B = 1,1,2-Triphenylethane-1,2-diol
  3. CA = Ethyl 2-hydroxy-2-phenylethanoate ; B = 2-Hydroxy-1,2-diphenylethan-1-one
  4. DA = 2-Ethoxy-2-phenylethanoic acid ; B = 2-Ethoxy-1,1,2-triphenylethan-1-ol

Correct answer

B. A = Ethyl 2-hydroxy-2-phenylethanoate ; B = 1,1,2-Triphenylethane-1,2-diol

Step-by-step solution

Benzaldehyde ( PhCHO ) reacts with NaCN to undergo nucleophilic addition, forming a cyanohydrin (mandelonitrile, PhCH ( OH ) CN ). Treatment of the cyanohydrin with ethanol and acid ( H ₃ O ^ ) hydrolyzes the nitrile group and simultaneously esterifies it, yielding ethyl 2-hydroxy-2-phenylethanoate (compound A). The ester group in compound A reacts with two equivalents of phenylmagnesium bromide ( PhMgBr ). The first equivalent undergoes nucleophilic acyl substitution to form a ketone intermediate, and the second e

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