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JEE Main levelSingle correct optionDifficulty 2 of 3co069

Phenylglyoxal, $C X_{6} H X_{5} COCHO$ , is treated with concentrated NaOH and the mixture is then acidified. The product is

A2-oxo-2-phenylethanoic acid
Bbenzoic acid
C2-hydroxy-1-phenylethanone
D2-hydroxy-2-phenylethanoic acid

Answer: D

The aldehyde carbon is hydrated by

OH X^{-}

and delivers hydride internally to the adjacent ketone carbon. The ketone carbon becomes

CH (OH)

and the aldehyde carbon becomes

COO X^{-}

. Acidification gives

C X_{6} H X_{5} CH (OH) COOH

, mandelic acid.

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