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JEE MainChemistryAldehydes and Ketones

Consider the following reaction sequence: 5-oxohexanal (i) HO-CH ₂ -CH ₂ -OH (1 eq), dry HCl (ii) NaBH ₄ , EtOH (iii) H ₃ O ^+ Major Product The major product formed in the above reaction is:

Options

  1. A6-hydroxyhexan-2-one
  2. BHexane-1,5-diol
  3. C5-oxohexanoic acid
  4. D5-hydroxyhexanal

Correct answer

D. 5-hydroxyhexanal

Step-by-step solution

Aldehydes are more reactive towards nucleophilic addition than ketones due to less steric hindrance and greater electrophilicity of the carbonyl carbon. Step (i): When 5-oxohexanal is treated with 1 equivalent of ethylene glycol in the presence of dry HCl, the more reactive aldehyde group is selectively protected as a cyclic acetal, leaving the ketone group unreacted. Step (ii): Sodium borohydride ( NaBH ₄ ) reduces the free ketone group to a secondary alcohol. The acetal group is stable to basic/neutral reducing a

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