JEE Main levelSingle correct optionDifficulty 2 of 3co018
A mixture of benzaldehyde and benzophenone is shaken with saturated aqueous NaHSOX3. Which procedure gives back pure benzaldehyde?
AFilter off the crystalline bisulfite adduct, and decompose it with dilute acid or aqueous NaX2COX3
BAdd NaOH to the mixture and extract with ether
CFilter off the solid that forms from benzophenone and distil the filtrate
DShake with NaHSOX3 and distil directly, as both compounds form adducts
Answer: A
Benzaldehyde adds NaHSOX3 to give a solid hydroxysulfonate, while diaryl ketones are too hindered and conjugated to react. The adduct is filtered and treated with acid or carbonate, which reverses the addition and releases the aldehyde.