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NEETChemistryAldehydes and Ketones

When 3-pentanone is reacted with benzaldehyde in the presence of dilute NaOH and heat, a major cross-aldol product 'P' is formed. Compound 'P' is then subjected to reductive ozonolysis ( O₃ followed by Zn/H₂O ). Identify the two final products formed after ozonolysis.

Options

  1. ABenzoic acid and pentanoic acid
  2. BBenzaldehyde and pentane-2,3-dione
  3. CBenzaldehyde and 3-pentanone
  4. DPhenylacetaldehyde and butane-2,3-dione

Correct answer

B. Benzaldehyde and pentane-2,3-dione

Step-by-step solution

The first step is a cross-aldol condensation between 3-pentanone and benzaldehyde. 3-Pentanone ( CH₃-CH₂-CO-CH₂-CH₃ ) is a symmetrical ketone with -hydrogens at C2 and C4. In the presence of dilute NaOH, it forms an enolate at C2. This enolate acts as a nucleophile and attacks the electrophilic carbonyl carbon of benzaldehyde ( C₆H₅-CHO ). Heating the reaction mixture causes the intermediate -hydroxy ketone to undergo dehydration (loss of a water molecule), forming the , -unsaturated ketone 'P'. The structure of 'P

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